Willem Klein

Willem Klein (4 December 1912 – 1 August 1986), also known as Wim Klein or under his stage names Pascal and Willy Wortel, was a Dutch mental calculator, famous for being able to carry out very complicated calculations in his head very fast. On 27 August 1976, he calculated the 73rd root of a 500-digit number in 2 minutes and 43 seconds. This feat was recorded by the Guinness Book of Records. Provided by Wikipedia