Simple integer encryption

Question

Is there a simple algorithm to encrypt integers? That is, a function E(i,k) that accepts an n-bit integer and a key (of any type) and produces another, unrelated n-bit integ

Answer 1

How about XORing it with a prime or two? Swapping bits around seems very random when trying to analyze it.
Try something along the lines of XORing it with a prime and itself after bit shifting.