Zerah Colburn (1804-1839) was a child prodigy of the 19th century who gained fame as a mental calculator.
He was born in Cabot, Vermont in 1804 and educated at Westminster School in London. He was thought to be mentally retarded until the age of seven. However, after six weeks of schooling his father overheard him repeating his multiplication tables. His father wasn't sure whether or not he learned the tables from his older brothers and sisters but he decided to test him further on his mathematical abilities and discovered that there was something special about his son when Zerah correctly multiplied 13 and 97.
Colburn's abilities developed rapidly and he was soon able to solve such problems as the number of seconds in 2,000 years, the product of 12,225 and 1,223, or the square root of 1,449. When he was seven years old he took six seconds to give the numbers of hours in thirty-eight years, two months, and seven days.
Zerah is reported to have been able to solve fairly complex problems. For example, the sixth number of Fermat is 2^(2^5)+1. The question is whether this number, 4294967297, is prime or not. Zerah calculated in his head that it was not and has divisor 641. The other divisor is 6700417 and can easily be found using a calculator.
His father soon began to capitalize on his boy's talents by taking Zerah around the country and eventually abroad, demonstrating the boy's exceptional abilities and also trying to find patrons who would pay for Zerah's education. His father was not very successful in finding patronage for Zerah's education and the patrons he did find he ultimately alienated. Therefore Zerah's schooling was rather irregular. In spite of his unconventional schooling, he also showed extreme talent in languages. Some credit a youthful competition he had with William Rowan Hamilton as an inspiration to him becoming a mathematician.[1] He died in 1839.
Despite all that, Colburn's abilities did not translate to adult achievement. He never had great success in any of his careers. The career of most note might be doing calculations for Dr. Thomas Young at the Board of Longitude, for a time, but mostly he drifted among several unsuccessful careers. These ranged from a mathematician, a teacher of languages and literature and even a Methodist preacher. In adulthood his abilities apparently declined to some degree. His nephew, also named Zerah Colburn, was a noted locomotive engineer and technical journalist.