Definition

Euler’s function, an arithmetic function, $\phi(n)$ finds the number of positive numbers less than $n$ and coprime to $n$ this function is defined as follows: $$\frac{\phi(n)}{n}=\prod_{p|n}\left( 1-\frac{1}{p} \right)$$where $p$ are the distinct prime numbers dividing $n$. Consequently, the function is Multiplicative.