Shakuntala Devi (November 4, 1929 – April 21, 2013) was a mental calculator who travel around the World showing her arithmetic talent.
According to Wikipedia:
Examples of the problems presented to Devi included calculating the cube root of 61,629,875, and the seventh root of 170,859,375. […] Devi provided the solution to the aforementioned problems (395 and 15, respectively) before [prof. Arthur] Jensen could copy them down in his notebook.
In the 1982 Guinness Book of Records is mentioned that on June 18, 1980, she demonstrated the multiplication of two 13-digit numbers—7,686,369,774,870 × 2,465,099,745,779—picked at random by the Computer Department of Imperial College, London. She correctly answered 18,947,668,177,995,426,462,773,730 in 28 seconds.
This doddle was published last year to commemorate Devi’s 84th birthday in a lot of countries of the World.