An illuminating, millennia-spanning history of the impact mathematics has had on the world, and the fascinating people who have mastered its inherent power, from Babylonian tax officials to the Apollo astronauts to the eccentric professor who invented the infrastructure of the online world. Counting is not innate to our nature, and without education humans can rarely count past three--beyond that, it's just "more." But once harnessed by our ancestors, the power of numbers allowed humanity to flourish in ways that continue to lead to discoveries and enrich our lives today. Ancient tax collectors used basic numeracy to fuel the growth of early civilization, navigators used clever geometrical tricks to engage in trade and connect people across vast distances, astronomers used logarithms to unlock the secrets of the heavens, and their descendants put them to use to land us on the moon. In every case, mathematics has proved to be a greatly underappreciated engine of human progress.