http://www.cplusplus.com/reference/limits/numeric_limits/ std::numeric_limits<unsigned long long int>::max() hitting gnome-calc, a 64bit integral should be able to hold 20! as 2^64 > 20!. However, this gcc doc might help if my usage of math skills are lacking https://gcc.gnu.org/onlinedocs/gcc/_005f_005fint128.html Michael To unsubscribe send a blank message to linux+unsubscribe [ at ] linux-ottawa [ dot ] org To get help send a blank message to linux+help [ at ] linux-ottawa [ dot ] org To visit the archives: https://lists.linux-ottawa.org