""Mathematics is the queen of the sciences and number theory is the queen of mathematics." Number theory is a fascinating branch of pure mathematics. It is concerned with the properties of, and the relationships between, positive integers. The history of number theory is populated by some of the most famous mathematicians of all time -- Euclid, Carl Friedrich Gauss, Pierre de Fermat, Leonhard Euler, Joseph-Louis Lagrange, G.H. Hardy, John Littlewood, Srinivasa Ramanujan, and of course Bernhard Riemann -- as well as many modern-day mathematical superstars, such as Andrew Wiles, Terence Tao, Barry Mazur, Yitang Zhang, and James Maynard to name but a few. And number theory includes some of the most famous mathematical theorems and problems too, from Fermat's last theorem and the twin prime conjecture to Goldbach's conjecture and, the granddaddy of them all, the Riemann hypothesis. The common practice of number theorists is one of chalk dust and blackboards, theorems and proofs, which can seem a world apart from more empirical explorations of data science.