1. Prove that if p E N is a prime and v E N is such that p | n, then (p-1)p-1 | o(n). Hint: When p is prime, what is (p)? 2. Using the previous question, prove that if (n) = 4, then n cannot be divisible by a prime p 7. Also prove that 3, 5 | n. 3. Find all n such that (n) Hint: Think in terms of the factorisation of n. You should find that there are four such n but you are required to prove this as part of this question! = 4.