After a great deal of brow-furrowing and lip-chewing, he calculated the answer to be 2,407,899,893,032,210.
Alexis Lemaire, 27, yesterday broke the world speed record for calculating the 13th root - the number that must be multiplied 13 times by itself to reach a solution - of a randomly generated 200 digit number.
The French artificial intelligence student achieved the extraordinary feat of mental arithmetic in just 70.2 seconds, beating his own previous record of 72.4 seconds.