Summary: This paper notes that Riemann contributed to almost all areas of mathematics, perceiving it from an analytic point of view, and influencing subjects as diverse as number theory and geometry. His lecture in 1854 is said to have revolutionised geometrical thinking beyond the conceptual Euclidean framework, as the basis for the general theory of relativity. His paper in 1859 was about the number of primes less than a given magnitude, now known as the prime number theorem. He also formulated the Riemann hypothesis about the zeroes of a function, and some see this as the central problem of pure mathematics.