Prove the statement $\phi(p) + \sigma(p) = p \cdot \tau(p)$ if and only if $p$ is prime.
Any tips how can I prove both sides? Thanks.
Prove the statement $\phi(p) + \sigma(p) = p \cdot \tau(p)$ if and only if $p$ is prime.
Any tips how can I prove both sides? Thanks.