Paul Erdos

Paul Erdos was a Hungarian mathematician renowned both for his prolific output, publishing around 1,500 papers across his career, and for an unusually collaborative, itinerant style of working, traveling constantly between colleagues' homes and universities around the world with few permanent possessions. He made foundational contributions to combinatorics, graph theory and number theory, and he pioneered the probabilistic method, a technique for proving that a mathematical object with certain properties must exist by showing that a randomly constructed object has those properties with positive probability, a tool that became widely used across combinatorics afterward. Erdos collaborated with more mathematicians than perhaps anyone in the field's history, more than 500 by some counts, a pattern later formalized informally as the Erdos number, measuring a mathematician's collaborative distance from Erdos himself through chains of co-authorship. He was known for offering small cash prizes, typically a few dollars to a few hundred dollars depending on the problem's difficulty, for the solution of mathematical problems he posed, several of which remained unsolved for years after his death in 1996.