<human>:  What is the name of the character who is a mathematician in the book ‘The Man Who Knew Infinity’?
<bot>: The character in the book The Man Who Knew Infinity is Ramanujan. Ramanujan was a brilliant Indian mathematician who worked in the field of number theory. He made important contributions to the theory of numbers, including the proof of Fermat's Last Theorem, the prime number theorem, and the theory of infinite series.