Am I safe to assume that the following idea is already part of how primes are determined to be prime?..
Prime Number = N
Divide N/2, this is the upper limit of the factoring process, = Nx
Start dividing N by Y (3, 4, 5 etc.),all the time reducing Nx by dividing it by the current value of Y.
At some point Y=Nx and if you haven't found it to be divisible, then you have a prime#
(Apologies to any mathematicians out there, I failed A level :) )