Given two odd primes, $p\neq q$, prove that there are no primitive roots $\mod(pq)$ 
Given two odd primes, $p\neq q$, prove that there are no primitive roots $\mod(pq)$

I don't know where to start with this, any help would be appreciated.

Hints:


*

*$\phi(pq)$ is an even multiple of both $\phi(p)=p-1$ and $\phi(q)=q-1$.

*Check what happens when you raise a residue class to power $\phi(pq)/2$.

