1. The problem statement, all variables and given/known data Let phi denote Euler's totient function, ie for k in N, phi(k) is the number of natural numbers less than k which are relatively prime to k. Prove that for every n in N we have n| phi((2^n) -1). (Hint: Compute o in U_(2^n)-1, the group of units in Z mod (2^n)-1) 3. The attempt at a solution I understand that in the hint, o=n...but I don't know how to relate it to the problem. I also found that the value of phi(k) for any k is an even integer.