diff --git a/autotests/folding/test.c.fold b/autotests/folding/test.c.fold
--- a/autotests/folding/test.c.fold
+++ b/autotests/folding/test.c.fold
@@ -8,14 +8,14 @@
 two \
 three
 
-static uint64_t intWithSuffix = 42ull;
+static uint64_t intWithSuffix = 42ull + ~1233L;
 static int octNum = 07232;
 static int invalidOctNum = 09231;
 static uint64_t hexNum = 0xDEADBEEF42;
 static uint64_t invalidHexNum = 0xGLDFKG;
 static char binNum = 0b0101010;
 
-static double d1 = 42.;
+static double d1 = 42. + 0x1.5p+2;
 static double d2 = .42;
 static double d3 = 42.3e1;
 static double d4 = .2e-12;
diff --git a/autotests/html/test.c.html b/autotests/html/test.c.html
--- a/autotests/html/test.c.html
+++ b/autotests/html/test.c.html
@@ -14,19 +14,19 @@
 <span style="color:#006e28;">two \</span>
 <span style="color:#006e28;">three</span>
 
-<span style="color:#0057ae;">static</span> <span style="color:#0057ae;">uint64_t</span> intWithSuffix = <span style="color:#b08000;">42ull</span>;
+<span style="color:#0057ae;">static</span> <span style="color:#0057ae;">uint64_t</span> intWithSuffix = <span style="color:#b08000;">42</span><span style="color:#644a9b;font-weight:bold;">ull</span> + ~<span style="color:#b08000;">1233</span><span style="color:#644a9b;font-weight:bold;">L</span>;
 <span style="color:#0057ae;">static</span> <span style="color:#0057ae;">int</span> octNum = <span style="color:#b08000;">07232</span>;
-<span style="color:#0057ae;">static</span> <span style="color:#0057ae;">int</span> invalidOctNum = <span style="color:#b08000;">09231</span>;
+<span style="color:#0057ae;">static</span> <span style="color:#0057ae;">int</span> invalidOctNum = <span style="color:#bf0303;text-decoration:underline;">09231</span>;
 <span style="color:#0057ae;">static</span> <span style="color:#0057ae;">uint64_t</span> hexNum = <span style="color:#b08000;">0xDEADBEEF42</span>;
-<span style="color:#0057ae;">static</span> <span style="color:#0057ae;">uint64_t</span> invalidHexNum = <span style="color:#b08000;">0</span>xGLDFKG;
+<span style="color:#0057ae;">static</span> <span style="color:#0057ae;">uint64_t</span> invalidHexNum = <span style="color:#bf0303;text-decoration:underline;">0xGLDFKG</span>;
 <span style="color:#0057ae;">static</span> <span style="color:#0057ae;">char</span> binNum = <span style="color:#b08000;">0b0101010</span>;
 
-<span style="color:#0057ae;">static</span> <span style="color:#0057ae;">double</span> d1 = <span style="color:#b08000;">42.</span>;
+<span style="color:#0057ae;">static</span> <span style="color:#0057ae;">double</span> d1 = <span style="color:#b08000;">42.</span> + <span style="color:#b08000;">0x1.5p+2</span>;
 <span style="color:#0057ae;">static</span> <span style="color:#0057ae;">double</span> d2 = <span style="color:#b08000;">.42</span>;
 <span style="color:#0057ae;">static</span> <span style="color:#0057ae;">double</span> d3 = <span style="color:#b08000;">42.3e1</span>;
 <span style="color:#0057ae;">static</span> <span style="color:#0057ae;">double</span> d4 = <span style="color:#b08000;">.2e-12</span>;
 <span style="color:#0057ae;">static</span> <span style="color:#0057ae;">double</span> d5 = <span style="color:#b08000;">32.e+12</span>;
-<span style="color:#0057ae;">static</span> <span style="color:#0057ae;">float</span> floatQualifier = <span style="color:#b08000;">23.123f</span>;
+<span style="color:#0057ae;">static</span> <span style="color:#0057ae;">float</span> floatQualifier = <span style="color:#b08000;">23.123</span><span style="color:#644a9b;font-weight:bold;">f</span>;
 
 <span style="color:#0057ae;">static</span> <span style="color:#0057ae;">const</span> <span style="color:#0057ae;">char</span> c1 = <span style="color:#924c9d;">'c'</span>;
 <span style="color:#0057ae;">static</span> <span style="color:#0057ae;">const</span> <span style="color:#0057ae;">char</span> c2 = <span style="color:#924c9d;">'\n'</span>;
diff --git a/autotests/input/test.c b/autotests/input/test.c
--- a/autotests/input/test.c
+++ b/autotests/input/test.c
@@ -8,14 +8,14 @@
 two \
 three
 
-static uint64_t intWithSuffix = 42ull;
+static uint64_t intWithSuffix = 42ull + ~1233L;
 static int octNum = 07232;
 static int invalidOctNum = 09231;
 static uint64_t hexNum = 0xDEADBEEF42;
 static uint64_t invalidHexNum = 0xGLDFKG;
 static char binNum = 0b0101010;
 
-static double d1 = 42.;
+static double d1 = 42. + 0x1.5p+2;
 static double d2 = .42;
 static double d3 = 42.3e1;
 static double d4 = .2e-12;
diff --git a/autotests/reference/test.c.ref b/autotests/reference/test.c.ref
--- a/autotests/reference/test.c.ref
+++ b/autotests/reference/test.c.ref
@@ -8,19 +8,19 @@
 <Preprocessor>two \</Preprocessor><br/>
 <Preprocessor>three</Preprocessor><br/>
 <Normal Text></Normal Text><br/>
-<Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>uint64_t</Data Type><Normal Text> intWithSuffix </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Decimal>42ull</Decimal><Symbol>;</Symbol><br/>
+<Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>uint64_t</Data Type><Normal Text> intWithSuffix </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Decimal>42</Decimal><Standard Suffix>ull</Standard Suffix><Normal Text> </Normal Text><Symbol>+</Symbol><Normal Text> </Normal Text><Symbol>~</Symbol><Decimal>1233</Decimal><Standard Suffix>L</Standard Suffix><Symbol>;</Symbol><br/>
 <Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>int</Data Type><Normal Text> octNum </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Octal>07232</Octal><Symbol>;</Symbol><br/>
-<Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>int</Data Type><Normal Text> invalidOctNum </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Decimal>09231</Decimal><Symbol>;</Symbol><br/>
+<Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>int</Data Type><Normal Text> invalidOctNum </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Error>09231</Error><Symbol>;</Symbol><br/>
 <Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>uint64_t</Data Type><Normal Text> hexNum </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Hex>0xDEADBEEF42</Hex><Symbol>;</Symbol><br/>
-<Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>uint64_t</Data Type><Normal Text> invalidHexNum </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Decimal>0</Decimal><Normal Text>xGLDFKG</Normal Text><Symbol>;</Symbol><br/>
+<Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>uint64_t</Data Type><Normal Text> invalidHexNum </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Error>0xGLDFKG</Error><Symbol>;</Symbol><br/>
 <Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>char</Data Type><Normal Text> binNum </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Binary>0b0101010</Binary><Symbol>;</Symbol><br/>
 <Normal Text></Normal Text><br/>
-<Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>double</Data Type><Normal Text> d1 </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Float>42.</Float><Symbol>;</Symbol><br/>
+<Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>double</Data Type><Normal Text> d1 </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Float>42.</Float><Normal Text> </Normal Text><Symbol>+</Symbol><Normal Text> </Normal Text><Float>0x1.5p+2</Float><Symbol>;</Symbol><br/>
 <Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>double</Data Type><Normal Text> d2 </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Float>.42</Float><Symbol>;</Symbol><br/>
 <Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>double</Data Type><Normal Text> d3 </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Float>42.3e1</Float><Symbol>;</Symbol><br/>
 <Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>double</Data Type><Normal Text> d4 </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Float>.2e-12</Float><Symbol>;</Symbol><br/>
 <Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>double</Data Type><Normal Text> d5 </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Float>32.e+12</Float><Symbol>;</Symbol><br/>
-<Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>float</Data Type><Normal Text> floatQualifier </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Float>23.123f</Float><Symbol>;</Symbol><br/>
+<Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>float</Data Type><Normal Text> floatQualifier </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Float>23.123</Float><Standard Suffix>f</Standard Suffix><Symbol>;</Symbol><br/>
 <Normal Text></Normal Text><br/>
 <Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>const</Data Type><Normal Text> </Normal Text><Data Type>char</Data Type><Normal Text> c1 </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Char>'c'</Char><Symbol>;</Symbol><br/>
 <Data Type>static</Data Type><Normal Text> </Normal Text><Data Type>const</Data Type><Normal Text> </Normal Text><Data Type>char</Data Type><Normal Text> c2 </Normal Text><Symbol>=</Symbol><Normal Text> </Normal Text><Char>'\n'</Char><Symbol>;</Symbol><br/>
diff --git a/data/syntax/c.xml b/data/syntax/c.xml
--- a/data/syntax/c.xml
+++ b/data/syntax/c.xml
@@ -1,17 +1,24 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE language SYSTEM "language.dtd">
+<!DOCTYPE language SYSTEM "language.dtd"
+[
+    <!ENTITY int "(?:[0-9](?:'?[0-9]+)*)">
+    <!ENTITY hex_int "(?:[0-9A-Fa-f](?:'?[0-9A-Fa-f]+)*)">
+    <!ENTITY exp_float "(?:[eE][+-]?&int;)">
+    <!ENTITY exp_hexfloat "(?:[pP][-+]?&int;)">
+]>
 <language name="C" section="Sources"
-          version="5" kateversion="5.0"
+          version="6" kateversion="5.0"
           indenter="cstyle"
           extensions="*.c;*.C;*.h"
           mimetype="text/x-csrc;text/x-c++src;text/x-chdr"
           priority="5">
 <!--
-##########################################################################
-## Fixes by Sebastian Pipping (webmaster@hartwork.org)
-##
-## NOTE: Keep in sync with C++ highlighter! (cpp.xml)
-##########################################################################
+
+    Fixes by Sebastian Pipping (webmaster@hartwork.org)
+
+    NOTE: Keep in sync with C++ highlighter! (cpp.xml)
+
+    Version 6: add more versatile numbers highlighting, taken from isocpp.xml
 -->
   <highlighting>
     <list name="controlflow">
@@ -119,34 +126,18 @@
         <DetectIdentifier />
         <DetectChar attribute="Symbol" context="#stay" char="{" beginRegion="Brace1" />
         <DetectChar attribute="Symbol" context="#stay" char="}" endRegion="Brace1" />
-        <Float attribute="Float" context="Float Suffixes"/>
-        <HlCOct attribute="Octal" context="#stay"/>
-        <HlCHex attribute="Hex" context="#stay"/>
-        <RegExpr attribute="Binary" context="#stay" String="0b[01]+[ul]{0,3}" insensitive="true" />
-        <Int attribute="Decimal" context="Int Suffixes"/>
+
+        <!-- Match numbers -->
+        <RegExpr attribute="Decimal" context="Number" String="\.?[0-9]" lookAhead="true" />
+
         <HlCChar attribute="Char" context="#stay"/>
         <DetectChar attribute="String" context="String" char="&quot;"/>
         <IncludeRules context="##Doxygen" />
         <Detect2Chars attribute="Comment" context="Commentar 1" char="/" char1="/"/>
         <Detect2Chars attribute="Comment" context="Commentar 2" char="/" char1="*" beginRegion="Comment"/>
         <AnyChar attribute="Symbol" context="#stay" String=":!%&amp;()+,-/.*&lt;=&gt;?[]|~^&#59;"/>
       </context>
 
-      <context name="Float Suffixes" attribute="Float" lineEndContext="#pop" fallthrough="true" fallthroughContext="#pop">
-          <AnyChar String="fF" attribute="Float" context="#pop"/>
-      </context>
-
-      <context name="Int Suffixes" attribute="Decimal" lineEndContext="#pop" fallthrough="true" fallthroughContext="#pop">
-          <StringDetect attribute="Decimal" context="#pop" String="ULL" insensitive="true"/>
-          <StringDetect attribute="Decimal" context="#pop" String="LUL" insensitive="true"/>
-          <StringDetect attribute="Decimal" context="#pop" String="LLU" insensitive="true"/>
-          <StringDetect attribute="Decimal" context="#pop" String="UL" insensitive="true"/>
-          <StringDetect attribute="Decimal" context="#pop" String="LU" insensitive="true"/>
-          <StringDetect attribute="Decimal" context="#pop" String="LL" insensitive="true"/>
-          <StringDetect attribute="Decimal" context="#pop" String="U" insensitive="true"/>
-          <StringDetect attribute="Decimal" context="#pop" String="L" insensitive="true"/>
-      </context>
-
       <context attribute="String" lineEndContext="#pop" name="String">
         <LineContinue attribute="String" context="#stay"/>
         <HlCStringChar attribute="String Char" context="#stay"/>
@@ -173,7 +164,7 @@
         <RegExpr attribute="Preprocessor" context="Preprocessor" String="#\s*if(?:def|ndef)?(?=\s+\S)" insensitive="true" beginRegion="PP" firstNonSpace="true" />
         <RegExpr attribute="Preprocessor" context="Preprocessor" String="#\s*endif" insensitive="true" endRegion="PP" firstNonSpace="true" />
         <RegExpr attribute="Preprocessor" context="Define" String="#\s*define.*((?=\\))" insensitive="true" firstNonSpace="true" />
-        
+
         <!-- folding for apple style #pragma mark - label -->
         <RegExpr attribute="Preprocessor" context="Preprocessor" String="#\s*pragma\s+mark\s+-\s*$" insensitive="true" firstNonSpace="true" endRegion="pragma_mark" />
         <RegExpr attribute="Preprocessor" context="Preprocessor" String="#\s*pragma\s+mark" insensitive="true" firstNonSpace="true" endRegion="pragma_mark" beginRegion="pragma_mark" />
@@ -228,6 +219,36 @@
         <RegExpr attribute="Comment" context="Outscoped intern" String="#\s*if" beginRegion="PP" firstNonSpace="true" />
         <RegExpr attribute="Comment" context="#pop" String="#\s*endif" endRegion="PP" firstNonSpace="true" />
       </context>
+
+      <context name="Number" attribute="Normal Text" lineEndContext="#pop" fallthrough="true" fallthroughContext="#pop">
+        <RegExpr attribute="Float" context="FloatSuffix" String="\.&int;&exp_float;?|&int;(?:&exp_float;|\.&int;?&exp_float;?)|0[xX](?:\.&hex_int;&exp_hexfloat;?|&hex_int;(?:&exp_hexfloat;|\.&hex_int;?&exp_hexfloat;?))" />
+        <IncludeRules context="Integer" />
+      </context>
+
+      <context name="Integer" attribute="Normal Text" lineEndContext="#pop" fallthrough="true" fallthroughContext="#pop">
+        <RegExpr attribute="Hex" context="IntSuffix" String="0[xX]&hex_int;" />
+        <RegExpr attribute="Binary" context="IntSuffix" String="0[Bb][01](?:'?[01]+)*" />
+        <RegExpr attribute="Octal" context="IntSuffix" String="0(?:'?[0-7]+)+" />
+        <RegExpr attribute="Decimal" context="IntSuffix" String="0(?![xXbB0-9])|[1-9](?:'?[0-9]+)*" />
+        <RegExpr attribute="Error" context="#pop" String="[._0-9A-Za-z']+" />
+      </context>
+
+      <context name="IntSuffix" attribute="Error" lineEndContext="#pop#pop" fallthrough="true" fallthroughContext="NumericSuffixError">
+        <DetectChar attribute="Error" context="#stay" char="'" />
+        <AnyChar attribute="Error" context="#pop!IntSuffixPattern" String="uUlLimunshyd_" lookAhead="true" />
+      </context>
+
+      <context name="IntSuffixPattern" attribute="Error" lineEndContext="#pop#pop" fallthrough="true" fallthroughContext="NumericSuffixError">
+        <RegExpr attribute="Standard Suffix" context="NumericSuffixError" String="[Uu][Ll]{0,2}|[Ll]{0,2}[Uu]?" />
+      </context>
+
+      <context name="FloatSuffix" attribute="Error" lineEndContext="#pop#pop" fallthrough="true" fallthroughContext="NumericSuffixError">
+        <AnyChar attribute="Standard Suffix" context="NumericSuffixError" String="fFlL" />
+      </context>
+
+      <context name="NumericSuffixError" attribute="Error" lineEndContext="#pop#pop#pop" fallthrough="true" fallthroughContext="#pop#pop#pop">
+        <RegExpr attribute="Error" context="#pop#pop#pop" String="\.[_0-9A-Za-z]*|[_0-9A-Za-z]+" />
+      </context>
     </contexts>
     <itemDatas>
       <itemData name="Normal Text"  defStyleNum="dsNormal" spellChecking="false"/>
@@ -239,6 +260,7 @@
       <itemData name="Hex"          defStyleNum="dsBaseN" spellChecking="false"/>
       <itemData name="Binary"       defStyleNum="dsBaseN" spellChecking="false"/>
       <itemData name="Float"        defStyleNum="dsFloat" spellChecking="false"/>
+      <itemData name="Standard Suffix" defStyleNum="dsBuiltIn" spellChecking="false" />
       <itemData name="Char"         defStyleNum="dsChar" spellChecking="false"/>
       <itemData name="String"       defStyleNum="dsString"/>
       <itemData name="String Char"  defStyleNum="dsSpecialChar"/>