Dear Physics Forum advisers, I am currently looking for an introductory textbook that covers the number theory without being too focused on the algebraic and analytical aspects of NT. My current underaduate research in the theoretical computer science and the Putnam preparation led me to the fascinating world of number theory. Basically, I am looking for one I can enrich my interest to the number theory, prepare for Putnam Competition, and aid my undergraduate research. I personally heard of the number theory books by Burton and Niven/Zuckerman/Montgomery, but I am not sure which will fit my purpose well. Could you recommend me some good books on the introductory number theory? My research adviser personally learned from the algebraic and analytic number theory textbooks, so he could not help me out since the books he read require a strong knowledge in the abstract algebra and complex analysis. I am currently studying the real analysis (Rudin, Apostol), abstract linear algebra (Hoffman/Kunze), and abstract algebra (Artin, little bits per day).