His life was devoted exclusively to mathematics. He traveled the world, jumping from conference to conference, research institution to research institution. At each location he proposed problems to be solved, informed listeners of problems he’d brought from other locations, and absorbed new problems from those nearby. If a problem went unsolved for a certain length of time, he would attach a monetary value to its solution, increasing as time extended, and pay whomever eventually solved it. Originally winners would not cash the check, instead mounting it on their office wall. With the advent of quality copiers, it became the copy that resides on the wall and the original went to the bank.
He had the money for this because he never had to spend any. A series of mathematicians around the world assumed responsibility for his comfort, providing meals, picking him up at the airport, carting him to conferences, and delivering him to the airport when he left for the next location and the next minder. He often stayed with the minders. When at one couples’ home, both excellent mathematicians, he would walk into their bedroom at 2:00 a.m. and say, “My mind is open.” That meant it was time to rise and do some mathematics.
He showed no hesitation about saying he could devote all of his time to mathematics because he had some condition that removed any interest in sex. He never explained what that condition was.
Once he wanted to ask me about something and suggested we go to lunch. I checked my wallet and found I could handle both our meals. It is the only time in my life I have seen a person do mathematics on a table cloth.
He rarely became angry. I was told, though, during the cold war when he was visiting this country, a “clever” reporter asked if he wasn’t happy to be in this free country. He blasted the reporter and said Hungary was his homeland and he loved it.
I first met him when he visited my university where a colleague and I had spent six months trying to prove a theorem that said, “If condition A was true, then condition B was.” Professor Erdös was prowling the halls and I invited him into my office, shaking. I explained the problem. He said nothing, then his head slumped and I thought the mathematical world was going to know me as the mathematician in whose office Paul Erdös died. Fortunately, he raised his head and said, “That may not be trivial. I will think about it.” The next morning he called me to say he had proven that what we wanted to show was almost never true!
He sent me a letter containing his proof. This was one of over 1500 letters he wrote that year, a number he authored every year! I am the lucky recipient of three, and I have them preserved in a special place.
At one conference I learned that this gentle man had one area of aggressive behavior. I foolishly stood between him and a buffet table. When they announced the food was ready, I was run over as he raced to get his fill.
He phoned me occasionally. He always called the office phone, never my own, and asked for me. The administrative assistant would run to my office to tell me, in awe, who was on the phone. It always terrified me. Would I be able to answer whatever he wanted or would I be exposed for the incompetent idiot I was? One time I couldn’t imagine what was the purpose of the call. When I picked up the phone he said, “Are you going to the conference next week?” and he mentioned a city. I admitted I was. He said, “I am too,” and he hung up. Weird, huh?
There’s something called an Erdös number. Erdös is the only one with Erdös number 0. If you have published a joint paper with Erdös your number is 1. If it isn’t 1 but you’ve published a paper with someone whose number is 1, then your number is 2. If it isn’t 1 or 2 but you’ve published a paper with someone whose number is 2, then your number is 3. And so forth. Mathematicians are proud of their Erdös numbers. Mine is 2.
Professor Paul Erdös died in 1996. I am so fortunate to have had a slight connection to this great man who never failed to ask about and show interest in my research.