List of books pertaining to number theory for all levels. Categorising them based on difficulty, beginner/intermediate/advanced would be helpful.
You could go to this page and search for books on the topic number theory. You can, if you wish, filter the search to include only books that have been reviewed. Please note that this page is part of a free trial period, and may become unavailable later.
Another source may be found here. This list is at least 10 years out of date, but anyone can access it. No reviews, except some books are marked with *s.
ETA: Here's another list of number theory books.