Microsoft Corp founder Bill Gates is the richest man again, overtaking investor Warren Buffett, as the global financial meltdown wiped out $2 trillion from the net worth of the world's billionaires, Forbes Magazine said.

The number of billionaires in the world fell by nearly a third to 793 in the past year, with large numbers dropping off the list in Russia, India and Turkey.

Gates regained his title as the richest man in the world, with $40 billion after slipping to third last year when he was worth $58 billion. Buffett, last year's richest man, fell to second place with $37 billion, down from $62 billion. Mexican telecommunications tycoon Carlos Slim took third place with $35 billion, down from $60 billion.