Shakuntala Devi (1929-2013), the subject of a new film released on Amazon Prime on Friday, has always been associated with an element of mystery. She was not formally educated, and was far from exceptional in cognitive tests, and yet she could perform calculations with large numbers in a few seconds, sometimes instantly. A look at her skills, and what is known about how she cultivated them:

So, what were her skills?

* Cube roots: It began with extracting cube roots of large numbers, which she could do in her head rapidly while still a child in the 1930s. Then in 1988, in a test of her abilities conducted by the psychologist Arthur Jensen at the University of California-Berkeley, Shakuntala Devi mentally calculated the cube roots of 95,443,993 (answer 457) in 2 seconds, of 204,336,469 (answer 589) in 5 seconds, and of 2,373,927,704 (answer 1334) in 10 seconds.