Wim Klein
Also known as Willem or William Klein and performed under several stage names, including Pascal, Moos Optel and Ali Ben Achmed.
Born 4 December 1912 in Amsterdam. Died 1 August 1986 (murdered in his Amsterdam apartment).
Employed by the Mathematisch Centrum, Amsterdam (1952-1956) and by CERN, Geneva (1958-1976).
Is one of the very best all-round mental calculators.
Claimed numerous "world records". Among them was the multiplication of two 40-digit numbers in 23 minutes. Klein's answer was incorrect - 13 of the 80 digits in the answer were wrong - but was more accurate than the previous best set in c1850 by Zacharias Dase, who erred in 27 digits.
Calculations Performed by Wim Klein
References/Links
1.
A Medico-Psychological Account, Followed by a Demonstration of a
Case of Supernormal Aptitude
Proceedings of the Second International Congress on Orthopedagogics,
1949
Berthold Stokvis PDF
2. World record root extraction PDF
3. SPIEGEL PDF