I decided to read up on Wim Klein. Klein worked as a physicist at CERN from 1958- 1976. He is considered to be one of the world's first human calculators. He worked at CERN at a time when there weren't many computers and because of this the scientists there greatly appreciated his ability to calculate calculations that may have taken much longer to complete without his help. Even the computers back then couldn't keep up with his calculations. When the computer eventually did become much smarter and faster it became Klein's job to make the equations inserted into the computer much simpler for it to read. He was an inspiration to future human calculators and will always be remembered as one of the best.

I calculate things really fast sometimes like this, but I don't think I could multiply three or four two digit numbers together in my head! Sometimes when my family and I are playing a bored game together and we have finished the game and are tallying scores I already know who won. It takes time for each person to individually add up their own score, but for me it's simple. My dad tells me to be quiet sometimes as I blurt out the scores and winner of each game we play. Maybe someday I will be able to multiply numbers like Klein.... but not today!

Source:
http://www.symmetrymagazine.org/article/december-2012/%E2%80%98human-calculator%E2%80%99-wim-klein-advanced-physics-inspired-others