For centuries, people have been fascinated by numbers. Numbers are familiar to everyone and form an essential foundation for our understanding of the world. Yet, the number system is not simply given to us; it has developed over millennia. Despite all the advancements, even today, any child can ask questions about numbers that no one can answer. Many unsolved problems related to numbers seem like quirky oddities of little use, while others hinder fundamental progress in important research areas of modern mathematics. Peter Higgins distills centuries of progress into an enlightening narrative that highlights the mysterious nature of numbers and explains how different types of numbers have emerged and why they are useful. The book includes many historical notes.