Hold my beer while I sum up each decimal placement and carry the number over.

At one point I had an audio book version of Surely You're Joking, Mr. Feynman. One of Richard Feynman's memoirs, he avoids talking about his work for the most part and tells stories in oddly low-level English about the shenanigans he'd get up to in his off hours. The entire book sounds something like this:

"One day I decided to go for a walk. I passed a bar. There was music playing in the bar, and people were dancing. It sounded great. I went inside to look at the girls. Their dancing looked great. I noticed one of the musicians was playing a little drum. I asked if I could try. He let me try the drum. It made a really interesting sound."

At one point, he was in a bar, and was approached by an abacus salesman, who challenged him to a math race. The abacus easily bested Feynman's mental math in addition, subtraction, multiplication and division, managed to outpace him in exponents and logarithms, and then it just so happened that as the math problems got harder, it just so happened that Feynman had the answers to the exact problems asked memorized, so it appeared he did them instantly in his head. Like by coincidence they asked the exact problem he'd spent the previous week calculating.