I have to calculate very large prime numbers. I'm stuck on the first step though.

That should be 2.32 * 10^77, but in my program it says something like 9395932912. If this isn't possible in C++, can someone tell me about any program that can check very large prime numbers?Code:unsigned long long int n = pow(2.0,257.0) - 1; cout << n;

Thankful for help.