thank you for not answering me, finally after all day of headache I found the right code: https://stackoverflow.com/questions/15196953/c-boost-large-number-storage this is finally working: #include <iostream> #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #pragma GCC diagnostic ignored "-Wfloat-equal" #include <boost/multiprecision/cpp_int.hpp> #pragma GCC diagnostic pop using namespace boost::multiprecision; int main() { cpp_int integer("314159265358979323846264338327950288419716"); integer *= 2; std::cout << integer << std::endl; } -- View this message in context: http://boost.2283326.n4.nabble.com/how-to-correctly-compile-and-use-math-mod... Sent from the Boost - Users mailing list archive at Nabble.com.