I'm looking for a good number theory book which doesn't hesitate to talk about the underlying algebra of some of the subject (e.g. using group theory to prove Fermat's Little Theorem and using ring theory to explain the ideas behind the Chinese Remainder Theorem). I'm still an undergraduate, so the book should be accessible to someone who has been through (or is going through, maybe) the standard undergrad abstract algebra coursework. The book closest to my description is one by Everest and Ward, which I own already. The problem is that it's a little short and they shove aside some of the algebra in the earlier chapters as well... Any suggestions?