2,397,207,667,966,701

Cosmos Magazine has a fascinating story about a "mathlete" named Alexis Lemaire who can do extremely complex math problems in his head. For instance:

"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."

Read the whole article.

Well now, how can you check this without knowing the 200-digit number? Even if you knew the 200-digit number, what computer would be able to do this mathematical feat in less than 72.4 seconds?

The comments on the forum where I saw this said:

* Wow. I use to tutor this kid...glad he FINALLY caught on.

* Lucky guess!

* the very same thing i do....only i just don’t blab it around a lot because see i don’t like to brag at all...

* See? He's got everybody fooled. Since most people don't have the means to check the answer, even if they knew the original 200-digit number. The correct answer is 2,397,207,667,966,747

* Chances of him using this trick to get a woman? 1 over 2,397,207,667,966,701

* How did he know how much is in my bank account???

* It’s the number of times your heart will beat in 60 million years.

* I thought it was 42.