In 1977, at Southern Methodist University, she 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.
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 event is mentioned in the 1982 Guinness Book of Records. Writer Steven Smith states that the result is "so far superior to anything previously reported that it can only be described as unbelievable".
Devi traveled the world demonstrating her arithmetic talents, including a tour of Europe in 1950 and a performance in New York City in 1976.
In 1988, she traveled to the U.S. to have her abilities studied by Arthur Jensen , a professor of psychology at the University of California, Berkeley .
Jensen tested her performance of several tasks, including the calculation of large numbers.
Examples of the problems presented to Devi included calculating the cube root of 61,629,875, and the seventh root of 170,859,375.
Jensen reported that Devi provided the solution to the aforementioned problems (395 and 15, respectively) before Jensen could copy them down in his notebook.
Jensen published his findings in the academic journal Intelligence in 1990.
Experience by Albert Einstein
Shakuntala Devi went on tours around the world starting in the ‘50s and performed in a number of institutions, theaters and on television up to the early 80’s.
During one such trip in the early 50’s, she met Albert Einstein. A reporter recounted the meet from Einstein’s note to Devi.
Albert Einstein says in the note, “I asked this woman a question which I take three hours to solve because I have to follow a whole method …. I know that nobody can do it in less time than I can… And the whole procedure has to be followed. The figures were so big that it took the whole board for her to write the answer. And before I had even finished the question, she started writing the answer.”
Einstein was absolutely puzzled. He asked, “How do you do it?”
Devi said, “I don’t know … — it simply happens. You ask me and figures start appearing before my eyes, somewhere inside. I can see 1, 2, 3, and I just go on writing…..”