# Erdös, Paul (1913–1996)

Paul Erdös was a Hungarian mathematician (his name is pronounced "AIR-dosh"), one of the greatest mathematicians of the twentieth century and, in terms of the number of papers published (more than 1,500), the most prolific in history – beating out even Leonhard Euler and inspiring the term "Erdös number." A mathematician has an Erdös number of 1 if he or she has published a paper with Erdös, of 2 if he or she has published with someone who published a paper with Erdös, and so on. Erdös worked almost non-stop, 19 hours a day, 7 days a week. "A mathematician," he quipped, "is a machine for turning coffee into theorems."

At age 20, Erdös discovered an elegant proof of a famous theorem in number theory, known as **Chebyshev's
theorem**, which says that for each number greater than one, there
is always at least one prime number between it and its double. Number theory remained one of his chief interests,
though his work spread across many fields, and he became renowned for posing
and solving problems that were often simple to state but notoriously difficult
to solve. He did groundbreaking work in a branch of mathematics known as Ramsey theory long before it became
fashionable in the late 1950s.

Bent and slight, often wearing sandals, Erdös had no time for the material side of life. "Property is nuisance," he said. Focused totally on mathematics, Erdos traveled from meeting to meeting, carrying a half-empty suitcase and staying with mathematicians wherever he went. His colleagues took care of him, lent him money, fed him, bought him clothes, and even did his taxes. In return, he showered them with ideas and challenges – with problems to be solved and brilliant ways of attacking them. Ernst Straus, who worked with both Albert Einstein and Erdös, wrote a tribute to Erdös shortly before his own death in 1983. He said of Erdös: "In our century, in which mathematics is so strongly dominated by 'theory doctors,' he has remained the prince of problem solvers and the absolute monarch of problem posers."

## Reference

1. Hoffman, Paul. *The Man Who Loved Only Numbers: The Story of Paul
Erdos and the Search for Mathematical Truth*. New York: Hyperion,
1998.