Fast thinking: Alexis Lemaire's calculation is checked by observers Bernadette Corcoran (R) and Linda Faulcon, 15 November 2007, at the New York Hall of Science. Lemaire calculated the 13th root of a 200-digit number in 72.438 seconds which is a world record time.

Credit: AFP

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NEW YORK: French "mathlete" Alexis Lemaire showed off his rare mental agility Thursday, claiming a new world record after working out in his head the 13th root of a random 200-digit number in just 72.4 seconds.

Lemaire, a 27-year-old doctoral student in artificial intelligence from Reims, near Paris, sat at a laptop computer that randomly selected the figure and displayed it on the screen. The number was so long it ran over 17 lines.

Lemaire, who says he doesn't consider himself a nerd or a geek, then took just over a minute to identify two quadrillion, 397 trillion, 207 billion, 667 million, 966 thousand, 701 as the 13th root. In other words, the number multiplied by itself 13 times produces the 200 digit number originally generated by the computer.

Complex numbers

"The first digit is very easy, the last digit is very easy, but the inside numbers are extremely difficult," said the mental gymnast after the performance at the New York Hall of Science a hands-on science centre in New York City, US.

Lemaire, who sports a beard and glasses under thickly-matted eyebrows and a furrowed brow, previously performed the feat in 77 seconds and has been working at the 13th root problem for years, repeatedly eroding his best time.

"I use an artificial intelligence system which I use on my own brain instead of on a computer," he explained, matter-of-factly. "Personally, I believe most people can do it but I have also a high-speed mind. My brain works sometimes very, very fast."

Lemaire said he first realised he had a knack for numbers when he was around 11 years old, but perhaps surprisingly he did not do well in maths at school. "I was not top of the class. I was an autodidact, mostly by books," he said.

He practices regularly and jogs every day, doesn't drink coffee or alcohol and avoids foods that are high in sugar or fat – to help him think faster.

"I use a process to improve my skills, to behave like a computer. When I do something wrong, I learn from that," he says. "It's like running a program in my head ... to control my brain," he says.

But he says he takes days off once in a while and listens to music to relax, although he is unable to name a band or a genre he actually likes. "It is important not to work too much," he said. "I can't do multiplication all day because otherwise my heart or my brain would fail. Too much training, thinking too fast could be bad for my health."

The human calculator

Lemaire has earned the nickname the "human calculator," but says with a rare smile he thinks the sobriquet of the "human computer" would be more accurate.

His nearest rival, he said, is a German whom he declines to name. But he claims to have no fear that other competitive mathematicians will successfully challenge him. "It is too difficult for them," he said, explaining that most of his rivals are only able to work out the 13th root of a 100-digit number.

He does not yet know what he will do when he finishes his PhD, but has been approached by banks and computer science companies keen to tap the power of his grey cells. "Many people at the banks think my gift can be very useful," he said.