Grigory Perelman's mathematical genius won the reclusive Russian a $1 million prize for solving what had been seen as the world's hardest problem. On Thursday, he turned it down.

In 2006, Perelman was due to collect the equivalent of $14,000 in Canadian dollars as the recipient of the Fields Medal, considered math's Nobel Prize. He turned it down.

In 1996, he was awarded a prize by the European Congress of Mathematicians. Yes, that's right: He turned it down.

He rejected the Clay Mathematics Institute's $1 million because he thought it was unfair and "unjust," saying that a U.S. mathematician deserved as much credit as he did, the Interfax news agency said.

The Cambridge, Mass., institute posted his rejection on its website and said it would wait until the fall before deciding what to do with the money.

Perelman's fame is due to his solving a riddle that has had mathematicians scratching their heads since 1904, when the Frenchman Henri Poincare posited that a three-dimensional sphere is the only such space that doesn't have holes.

The Russian attracted attention in 2003 when he posted papers on the Internet that later turned out to be proof of Poincare's theory. But Perelman refuses to take all the credit, saying he had built on the work of a Columbia University professor, Richard Hamilton.

The president of the Clay Institute, James Carlson, said that he had spoken with Perelman by phone and that he was, "as usual, quite pleasant" but "firm in his decision" not to accept its prize, The New York Times reported.

According to Interfax, Perelman said, "To put it short, the main reason is my disagreement with the organized mathematical community. I don't like their decisions. I consider them unjust."

Back in 2006, the then president of the International Mathematical Union, John Ball, said he had traveled to St. Petersburg, Russia, where Perelman lives in seclusion with his elderly mother, to try to better understand the Russian's reasons for rejecting awards.

Ball told the BBC he had spoken to Perelman about his differences with the mathematical community.

"However, I am unable to disclose these comments in public," Ball said, adding, "He has a different psychological makeup, which makes him see life differently."