Yes yes, Ramanujan is known as the man who loves numbers. Oddly enough, I think he spent his spare time thinking about numbers. While others worked with them, he probably sat there and tried to define what a number was and why is it a number.
Hmm thats strange, a prime number is usually useful for computer science people. It's there basic of cryptology. If you can write an algorithm to factor primes into a form 2^m-1. Where m is an integer, then you have the tools to crack a code.