3
$\begingroup$

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.

  • 0
    Could you give us more informations about the problem?2012-09-01
  • 0
    @primemiss that's correct: $(p-1) + (p+1) = p*2.$2012-09-01

2 Answers 2