You’re asked a math question you must solve entirely in your head. The answer is 2,396,232,838,850,303. What chance have you got of getting it right?

Alexis Lemaire with one of his little problems

Correct answer : zero.

Not, however, if you are Alexis Lemaire. He has broken the record for finding the 13th root of a 200-digit number. Basically, that looks like this :

85,877,066,894,718,045,602,549,144,850,158,599,
202,771,247,748,960,878,023,151,390,314,284,284,
465,842,798,373,290,242,826,571,823,153,045,030,
300,932,591,615,405,929,429,773,640,895,967,991,
430,381,763,526,613,357,308,674,592,650,724,521,
841,103,664,923,661,204,223.

Last December, at Oxford’s Museum of the History of Science Alexis broke his own record, reducing it to 77.99 seconds. Even with a calculator you wouldn’t beat Lemaire doing the calculation in his head.

How does he do it? “It is quite difficult. I did a lot of preparation for this. More than four years of work and a lot of training every day. A lot of memorizing. I need three things — calculating, memorizing and the third on mathematical skills. It is a lot of work and maybe a natural gift.”

One of the theories being put forward by researchers is that damage to one area of the brain creates compensation in another. Brain scientist Dr Allan Snyder has suggested that everyone may possess such abilities but be unable to access them.

The genius himself explains that what he does is to transform raw numbers into other structures so he can “see” the answer to the problem. “When I think of numbers sometimes I see a movie, sometimes sentences. I can translate the numbers into words. This is very important for me. The art is to convert memory chunks into some kind of structure.

“I see images, phrases, actions. It’s very tactile, sensitive. I have these associations between places and numbers. Some places are imaginary, I try to vary so I don’t confuse the numbers. It’s important to memorize. I have to be precise.”

Lemaire’s explanation is similar to that of British genius Daniel Tammet, who set the world record for reciting pi to more than 22,000 digits at the same museum in 2004. To him, he said, each number has a distinct colour and appearance, some beautiful, some not, with each complex calculation making up a landscape.

Now you know.