# Thread: Proving on Euler's totient?

1. ## Proving on Euler's totient?

The Euler's totient φ is known to be multiplicative. Let f be de_ned by f(n) = φ (φ (n)). Is the

2. ## Re: Proving on Euler's totient?

f will be multiplicative if gcd(a,b) = 1 implies gcd(φ(a),φ(b)) = 1. can you think of a counter-example? look at f(15).

3. ## Re: Proving on Euler's totient?

@musngiburger

since $\varphi(n)$ is always even for n>2 $gcd(\varphi(a),\varphi(b)) = 1$ never true !!!!!!