I have 2 problems that I need some help on if you guys would.

Show that phi(n)less than or equal to n, and phi(n)=n iff n=1.

and

For k> or equal to 2 show that if 2^k -1 is prime then n=(2^k-1)((2^k)-1) has o(n)=2n, where o(n) is sum of all positive divisors of n.

Thanks in advance for your help.