diff --git a/lib/checkuninitvar.cpp b/lib/checkuninitvar.cpp
index 469ff75d0..915246810 100644
--- a/lib/checkuninitvar.cpp
+++ b/lib/checkuninitvar.cpp
@@ -605,7 +605,7 @@ private:
                     if (Token::Match(tok.tokAt(6), "%num% )"))
                     {
                         const unsigned int len = Token::getStrLength(tok.tokAt(4));
-                        const long sz = MathLib::toLongNumber(tok.strAt(6));
+                        const MathLib::bigint sz = MathLib::toLongNumber(tok.strAt(6));
                         if (sz >= 0 && len >= static_cast<unsigned long>(sz))
                         {
                             init_strncpy(checks, tok.tokAt(2));
diff --git a/lib/mathlib.cpp b/lib/mathlib.cpp
index 57c9ad05c..22c04c0e3 100644
--- a/lib/mathlib.cpp
+++ b/lib/mathlib.cpp
@@ -30,23 +30,37 @@
 #include <cmath>
 #include <cctype>
 
-long MathLib::toLongNumber(const std::string &str)
+MathLib::bigint MathLib::toLongNumber(const std::string &str)
 {
+    // hexadecimal numbers:
     if (str.compare(0, 2, "0x") == 0
         || str.compare(0, 3, "+0x") == 0
         || str.compare(0, 3, "-0x") == 0)
     {
-        return std::strtol(str.c_str(), '\0', 16);
+        bigint ret = 0;
+        std::istringstream istr(str.substr((str[0]=='0') ? 2 : 3));
+        istr >> std::hex >> ret;
+        return (str[0]=='-') ? -ret : ret;
     }
+
+    // octal numbers:
     if (str.compare(0, 1, "0") == 0
         ||  str.compare(0, 2, "+0") == 0
         ||  str.compare(0, 2, "-0") == 0)
     {
-        return std::strtol(str.c_str(), '\0', 8);
+        bigint ret = 0;
+        std::istringstream istr(str.substr((str[0]=='0') ? 1 : 2));
+        istr >> std::oct >> ret;
+        return (str[0]=='-') ? -ret : ret;
     }
-    return (str.find("E", 0) != std::string::npos || str.find("e", 0) != std::string::npos)
-           ? static_cast<long>(std::atof(str.c_str()))
-           : std::atol(str.c_str());
+
+    if (str.find_first_of("eE") != std::string::npos)
+        return static_cast<bigint>(std::atof(str.c_str()));
+
+    bigint ret = 0;
+    std::istringstream istr(str);
+    istr >> ret;
+    return ret;
 }
 
 double MathLib::toDoubleNumber(const std::string &str)
@@ -199,7 +213,7 @@ std::string MathLib::add(const std::string & first, const std::string & second)
 {
     if (MathLib::isInt(first) && MathLib::isInt(second))
     {
-        return toString<long>(toLongNumber(first) + toLongNumber(second));
+        return toString<bigint>(toLongNumber(first) + toLongNumber(second));
     }
     return toString<double>(toDoubleNumber(first) + toDoubleNumber(second));
 }
@@ -208,7 +222,7 @@ std::string MathLib::subtract(const std::string &first, const std::string &secon
 {
     if (MathLib::isInt(first) && MathLib::isInt(second))
     {
-        return toString<long>(toLongNumber(first) - toLongNumber(second));
+        return toString<bigint>(toLongNumber(first) - toLongNumber(second));
     }
     return toString<double>(toDoubleNumber(first) - toDoubleNumber(second));
 }
@@ -217,7 +231,7 @@ std::string MathLib::divide(const std::string &first, const std::string &second)
 {
     if (MathLib::isInt(first) && MathLib::isInt(second))
     {
-        return toString<long>(toLongNumber(first) / toLongNumber(second));
+        return toString<bigint>(toLongNumber(first) / toLongNumber(second));
     }
     return toString<double>(toDoubleNumber(first) / toDoubleNumber(second));
 }
@@ -226,7 +240,7 @@ std::string MathLib::multiply(const std::string &first, const std::string &secon
 {
     if (MathLib::isInt(first) && MathLib::isInt(second))
     {
-        return toString<long>(toLongNumber(first) * toLongNumber(second));
+        return toString<bigint>(toLongNumber(first) * toLongNumber(second));
     }
     return toString<double>(toDoubleNumber(first) * toDoubleNumber(second));
 }
diff --git a/lib/mathlib.h b/lib/mathlib.h
index 1ff4f6ccd..717dd6116 100644
--- a/lib/mathlib.h
+++ b/lib/mathlib.h
@@ -33,7 +33,16 @@ class Tokenizer;
 class MathLib
 {
 public:
-    static long toLongNumber(const std::string & str);
+    // To compile Cppcheck on a compiler that doesn't support "long long",
+    // use NOLONGLONG.
+#ifdef NOLONGLONG
+    typedef long bigint;
+#else
+    typedef long long bigint;
+#endif
+
+
+    static bigint toLongNumber(const std::string & str);
     static double toDoubleNumber(const std::string & str);
 
     template<typename T>
diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index ef0f9f5e4..3bce12c26 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -6571,9 +6571,9 @@ bool Tokenizer::simplifyCalculations()
                 const std::string after(tok->tokAt(3) ? tok->strAt(3).c_str() : "");
                 if ((prev == "(" || prev == "&&" || prev == "||") && (after == ")" || after == "&&" || after == "||"))
                 {
-                    const int op1(MathLib::toLongNumber(tok->str()));
+                    const MathLib::bigint op1(MathLib::toLongNumber(tok->str()));
                     const std::string &cmp(tok->next()->str());
-                    const int op2(MathLib::toLongNumber(tok->tokAt(2)->str()));
+                    const MathLib::bigint op2(MathLib::toLongNumber(tok->tokAt(2)->str()));
 
                     std::string result;
 
@@ -6598,16 +6598,16 @@ bool Tokenizer::simplifyCalculations()
 
             if (Token::Match(tok->previous(), "[([,=] %num% <<|>> %num%"))
             {
-                const int op1(MathLib::toLongNumber(tok->str()));
-                const int op2(MathLib::toLongNumber(tok->tokAt(2)->str()));
-                int result;
+                const MathLib::bigint op1(MathLib::toLongNumber(tok->str()));
+                const MathLib::bigint op2(MathLib::toLongNumber(tok->tokAt(2)->str()));
+                MathLib::bigint result;
 
                 if (tok->next()->str() == "<<")
                     result = op1 << op2;
                 else
                     result = op1 >> op2;
 
-                std::stringstream ss;
+                std::ostringstream ss;
                 ss << result;
 
                 tok->str(ss.str());
@@ -7091,7 +7091,7 @@ void Tokenizer::simplifyEnum()
 
             end = tok1->tokAt(-1)->link();
 
-            long lastValue = -1;
+            MathLib::bigint lastValue = -1;
             Token * lastEnumValueStart = 0;
             Token * lastEnumValueEnd = 0;
 
@@ -7146,7 +7146,7 @@ void Tokenizer::simplifyEnum()
                         // value is previous expression + 1
                         tok1->insertToken("+");
                         tok1 = tok1->next();
-                        tok1->insertToken(MathLib::toString<long>(lastValue));
+                        tok1->insertToken(MathLib::toString<MathLib::bigint>(lastValue));
                         enumValue = 0;
                         enumValueStart = valueStart->next();
                         enumValueEnd = tok1->next();
@@ -7154,7 +7154,7 @@ void Tokenizer::simplifyEnum()
                     else
                     {
                         // value is previous numeric value + 1
-                        tok1->insertToken(MathLib::toString<long>(lastValue));
+                        tok1->insertToken(MathLib::toString<MathLib::bigint>(lastValue));
                         enumValue = tok1->next();
                     }
                 }
diff --git a/test/testmathlib.cpp b/test/testmathlib.cpp
index 55908f432..03086c227 100644
--- a/test/testmathlib.cpp
+++ b/test/testmathlib.cpp
@@ -68,7 +68,7 @@ private:
         ASSERT_EQUALS("-3000"           , MathLib::multiply("-1.0E+3", "3"));
         ASSERT_EQUALS("0" 	            , MathLib::multiply("-1.0E+3", "0"));
         ASSERT_EQUALS("0" 	            , MathLib::multiply("+1.0E+3", "0"));
-        TODO_ASSERT_EQUALS("2147483648" , MathLib::multiply("2","1073741824"));
+        ASSERT_EQUALS("2147483648" ,      MathLib::multiply("2","1073741824"));
         ASSERT_EQUALS("536870912"  , MathLib::multiply("512","1048576"));
 
         // divide