The book of the famous mathematician G. Hardy is dedicated to the life and scientific works of Ramanujan, a phenomenal Indian mathematician who became famous for his remarkable achievements in number theory. The translation is from the English edition of 1940. The book is written with Hardy's inherent mastery of presentation, which will make the deepest and most intricate questions of number theory understandable and accessible. For a wide range of readers - from professional mathematicians to lovers of non-standard mathematical problems.