How to store extremely large numbers?

Question

For example I have a factorial program that needs to save really huge integers that can be 50+ digits long. The absolute maximum primitive data type in C++ is unsigned

Answer 1

If you already have a boost dependency (which many people these days do), you can use the boost multi-precision library. In fact, it already has an example of a factorial program that can support output up to 128 bits, though extending it further is pretty trivial.