The abacus is still taught in Japanese schools, although not as intensively as it once was. But the centuries-old tool is still popular, and national tournaments attract elite competitors.

The caller read out the numbers at a speed evoking an auctioneer on fast-forward, each multidigit figure blurring into the next.

Within seconds, Daiki Kamino's right arm shot up in the air, triumphant. Not only had he heard every number, but he also had tabulated them and arrived at the correct, 16-digit sum: 8,186,699,633,530,061.

He did it all on an abacus.


For this bit of mathematical virtuosity, Daiki, 16, a high