Hello, I wonder if somebody could point me to a book (preferably), or paper, link, etc. which explores the relations between number theory and group theory. For example, I am (more or less) following Burton's "Elementary Number Theory" and there is no mention of groups. I also have the Hardy/Wright book as a reference, and there is no mention there either. Which is a pity, because I feel some subjects, or to put an example, Euler's totient function, or primitive roots, are better understood in the context of the multiplicative group modulo n.