The Indian mathematician Ramanujan Ramanujan and the theory of prime numbers Round numbers Some more problems of the analytic theory of numbers A lattice-point problem Ramanujan's work on partitions Hypergeometric series Asymptotic theory of partitions The representation of numbers as sums of squares Ramanujan's function $\tau(n)$ Definite integrals Elliptic and modular functions Bibliography.

Ramanujan occupies a unique place in analytic number theory. His formulas, identities, and calculations are still amazing three-quarters of a century after his death. Many of his discoveries seem to have appeared as if from the ether. The author collects twelve of his own lectures on topics stemming from Ramanujan's life and work.