Paul Erdös dedicated his life to problem-solving. The subject that drove him was math; everything else was secondary: he had no home, no set job, and no property. Everything he owned could fit inside a suitcase, which stayed mostly packed, as he traveled around the world to solve and pose math problems. He was known to visit fellow mathematicians and, eager to work, say, "My mind is open."

   Erdös was born in Budapest, Hungary, in 1913. His parents were math teachers and they recognized his gift when he was very young. He received a Ph.D. in mathematics from the University of Budapest, entering at age 17 and graduating only four years later. He made his first important mathematical discovery at just 20 years old.

   Erdös went on to become one of the most prolific mathematicians in the world, with over 1,400 published papers and hundreds of collaborators. He also created the field of discrete mathematics, which laid the foundation for today’s computer technology.

   Erdös, with all of his eccentricities, was easily accepted into colleagues’ home because he offered them plenty of new and challenging problems -- and methods for solving them. Many were co-authors on his works because he emphasized teamwork and believed math should be a social subject.

   The same goes for his work in universities around the world. Erdös was so respected that many prestigious universities allowed him to lecture for a few months, receive payment for his work, and move on. His appearances were irregular and he had no formal arrangements with any school.

   He was known to fly to as many as 15 places in one month lecturing, attending math conferences, and visiting and working with fellow mathematicians. Even at 83, he still spent most of his time traveling and working on problems until his death in 1996.

   Erdös touched the lives of so many mathematicians that they invented the term "Erdös number" to boast a connection with him. If someone co-authored a paper with Erdös, they would have an Erdös number of one. If they worked with someone else, that person would be a two, and so on.

   According to his obituary published on the first page of the New York Times, 458 people had an Erdös number of one; an additional 4,500 had an Erdös number of two. The highest number is 12, but there are very few high numbers because Erdös worked with so many people around the world.

   Paul Erdös understood that math was key to understanding the world around us. He also inspired others by encouraging teamwork, and he helped to financially support budding mathematicians in order to solve as many math problems as possible. A friend and fellow mathematician called him "the prince of problem solvers and the absolute monarch of problem posers."