Help with prime number and modulo
I have a question about performing a modulo with large prime numbers.
If I want to check if A^X + B^Y = C^Z, I was told to try the following filtering method:
(A^XmodN + B^YmodN)modN = C^ZmodN with two large values of N that are prime.
I dont understand the significance of the values of N being prime. Apparently this causes it to be a better filter than with values of N that are not prime.
Why is that? I only have very basic Math knowledge so please try and help me out.