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.