[SOLVED] Rusty about groups

Hi !

I've just learnt today that I studied a big part of group theory last year (Rofl)

So I have two questions that I knew the answer, but forgot it...

1/ Is the order of an element in an integer between m : , or , or , or ?

2/ How to prove that if , there is a unique (or <n, depending on the answer of the first question :P) such that ?

And here is an extra question :

3/ Basically, what's the difference between Carmichael's indicator and Euler's totient function ?

Thanks ;)