Nifty Tips

Posts Tagged ‘integer’

I know the easiest way of determining if an integer X is prime is to try every integer Y up to sqrt(X), and if X modulo Y = 0, then X is composite. That’s very basic.

What I want to know is, how do I test for primality faster than this? It’s easy to generate a prime number – they’re found at N!+1 where N is a positive integer. For instance, 9996!+1 is an extremely large prime. One would think the inverse of this function would be simple, and it is… but not all primes are found this way. For instance, 5 is prime but 4 is not the result of a factorial.

So… what’s the quickest way to determine if a number is prime (especially in a computer program)?

need to create an 8 bit unsigned integer in java. Would also like some help in using bit masks and bit shifting as I’m pretty sure that would be the answer to my original question.