The International Mathematics Federation has awarded its top prize, the Fields Medal, to a Russian mathematician who has declined to accept the award.
Grigory Perelman is believed to have solved the Poincare Conjecture, a 100-year-old riddle in the branch of mathematics known as topology, which deals with the shapes of objects.
The Federation's president John Ball told the International Congress of Mathematicians in Madrid Tuesday that Perelman refused the prize.
Three other medal winners from Australia, France, and Russia accepted their awards from Spain's King Juan Carlos
A separate $1-million award from the Clay Mathematics Institute in the northeastern U.S. state of Massachusetts may also be Perelman's for the taking, but he has shown no sign that he will claim that prize either.
Colleagues say they have not seen the reclusive Perelman since he left his post at St. Petersburg's Steklov Institute of Mathematics in January.
The Poincare Conjecture, first suggested by French mathematician Henri Poincare in 1904, essentially posits that a donut-shaped object cannot be manipulated into a sphere without tearing. It is one of the most important questions in the field of topology.
Perelman first began publishing a series of papers on the problem in 2002.
Some information for this report was provided by AFP, AP and Reuters.