Meet Chirag, the class eight student from Saharanpur, Uttar Pradesh, who has a unique grip on numbers. He can recite the multiplication table for any number, all the way up to 20 crore.

As the video above reveals, Chirag, egged on by one of his teachers at school, can now solve complex arithmetical problems without the help of a calculator or even a piece of paper.

“Human calculators”, as people with this skill are called, are able to tackle problems involving large numbers entirely in their heads. Many are born prodigies with this ability, while others train themselves. India’s most famous human calculator was, of course, Shakuntala Devi (1929 - 2013), who attained global fame for her feats.