This online calculator calculates factorial of a positive integer. Practically unlimited positive integer. In fact, it is limited only by the time you are willing to wait until calculation completes. I was patient enough to wait for 100000!

This article describes how to perform long or infinite calculations while allowing user to stop them

The calculator performs modular exponentiation of big numbers.

The calculator counts number of bits required to represent a number in the binary form. It also displays an input number in binary, octal, decimal, and hex forms.