546,372,891 ^ 23 (a 201 digit number)

In 1977,  at the Southern Methodist University, Shakuntala Devi (November 4, 1929 – April 21, 2013), popularly known as "Human Computer", was asked to give the 23rd root of a 201-digit number; she answered in 50 seconds. Her answer—546,372,891—was confirmed by calculations done at the U.S. Bureau of Standards by the Univac 1101 computer, for which a special program had to be written to perform such a large calculation.