We investigate some equations involving the number of divisors d(n); sum σ(n); Euler's totient function ϕ(n); distinct prime factors ω(n); and all (counted with multiplicity) Ω(n). The first part deals equation f(xy) + f(xz) = f(yz). In second part, as an analogy to x2 y2 z2, we study f(x2) f(y2) f(z2) its generalization higher degrees more terms. use just elementary methods basic facts about a...