Natural numbers are the oldest human inventions. This volume describes their nature, laws, history and current status. The first five chapters contain not only the basics of elementary number theory for the convenience of teaching and continuity of reading, but also many latest research results. For the first time in history, the Chinese Remainder Theorem is renamed the Qin Jiushao Theorem to give him the full credit for his establishment of this famous theorem in number theory. Chapter 6 is about the fascinating congruence modulo an integer power, and Chapter 7 introduces a new problem extracted by the author from the classical problems of number theory, which is out of the combination of additive number theory and multiplicative number theory.In this volume, there is supplementary material after each section to broaden the reader's knowledge and imagination. It either discusses the rudiments of some aspects or introduces new topics, such as the perfect number problem, Goldbach's conjecture, the twin prime conjecture, the 3x + 1 problem, Waring's problem, Catalan's conjecture, Euler's conjecture, Fermat's Last Theorem, etc.Originally published in Chinese as in 2014, The Book on Numbers is written for anyone who loves natural numbers. The author is not only a mathematician, but also a literary and science writer, with more than 20 books published, many of which were translated into 20 languages.