Prove that phee(n) is even for any n greater than or equal to 3 (here phee(n) is the Euler phee-
function).
What do you know about ?
If you know that for , then:
And it follows immeadiatly that if that is even (as if it has an odd prime factor , then is even and so is even, or if it only has even prime factors then it is a power k of 2 greater than the first and is even)