According to the latest list of world's top billionaires published by the Forbes magazine, Mexican billionaire Carlos Slim is the richest person in the world with 53.5 billion dollars assets, while Indian industrialist Mukesh Ambani ranks fourth with 29 billion dollars. Slim is followed by Bill Gates with a net worth of 53 billion dollars and Warren Buffet at the third spot with assets worth 47 billion dollars. NRI billionaire Lakshmi Mittal with a net worth of 28.7 billion ranks fifth. There are 1,011 billionaires in the world now, up from 793 a year ago.