Euler’s totient is the function that returns how many numbers smaller than x, are Coprime with x.
Prime Property
If is prime:
Composite Property
If , where and are prime numbers:
ϕ(x)=∑n<x;n is relatively prime with x Euler’s totient is the function that returns how many numbers smaller than x, are Coprime with x.
If x is prime: ϕ(x)=x−1
If x=p∗q, where p and q are prime numbers: ϕ(x)=ϕ(p)∗ϕ(q)=(p−1)(q−1)
ϕ(xn)=xn−xn−1