Based on lectures given by Professor Hlawka in Vienna and in Pasadena, the book covers diophantine approximation, uniform distribution of numbers modulo 1 and geometry of numbers, as well as analytic number theory. It also proves the irrationality of zeta (3) and presents the important method of A. and H. Lenstra for the decomposition of polynomials, neither available in any other textbook. Various proofs of the prime number theorem are described. This monograph on number theory, real analysis, algebra/algebraic number theory is intended for students and lecturers in the above fields.