It is hard to exaggerate Mr Erdös’s passion. For 19 hours a day, seven days a week, stimulated by coffee, and later by amphetamines, he worked on mathematics. He might start a game of chess, but would probably doze off until the conversation returned to maths. To find another life this century as intensely devoted to abstraction, one must reach back to Ludwig Wittgenstein (1889-1951), who stripped his life bare for philosophy. But whereas Wittgenstein discarded his family fortune as a form of self-torture, Mr Erdös gave away most of the money he earned because he simply did not need it. “Private property is a nuisance,” he would say. And where Wittgenstein was driven by near suicidal compulsions, Mr Erdös simply constructed his life to extract from his magnificent obsession the maximum amount of happiness.
Source; there’s much else on the site.
Also here are personal reminiscences. Fun to think how, in 60 years time or so, we’ll be seeing the deaths of the last mathematicians who worked with him directly. The last people who really knew (i.e. who worked with) the man himself.