This is a translation of Landau's famous Elementare Zahlentheorie with added exercises by Paul T. Bateman and Eugene E. Kohlbecker. This three-volume classic work is reprinted here as a single volume
For an "elementary" textbook, contains some pretty interesting "intermediate" topics. Includes an elementary proof of the prime number theorem (but instead of the tight result of Hadamard and Poussin, gets a range like 3/4 < pi(x)*log(x)/x < 5/4).