The number he had to calculate the cube root of was 718,237,140,592.542,803,123,253,912,561,466,729. “The first thing I looked at was the last four numbers. Then I can immediately tell what the last three digits of the answer are. There is a very clear structure in the numbers, I’ve been working on that for 70 years, I can just see that,” Bouman explains afterwards. He is calculating every day. “There is something compulsive about it. When I cycle and I see a telephone number on a truck, I start calculating. When I see a ship with a registration number, I see if I can factor that number, I can’t stop that. It’s on my hard drive. If you want me to stop, you must separate my head from my torso.”
The first assignment Bouman had been given on Saturday went wrong, he gave the wrong answer. Then he got the new number. “You are automatically a bit stressed, people have expectations of you. I realized fairly quickly that the first attempt went wrong. I’ll take a look later to see if I can find the nature of the short circuit. For a problem you have to make a generous number of different calculations, so the possibilities for errors are plentiful. I have trained for months, in almost all cases this goes well.”
top sport
Because the first attempt was unsuccessful, Bouman took a little more time on his second attempt. “That assignment was just a little bit better, I had the momentum. At the end I slowed down a bit, because I didn’t want to make a second mistake. I constantly check the calculations. I don’t care about time, I just think about the right answer.”
That correct answer was 895,548,862,009. Bouman looks back on his performance with satisfaction. “Mental arithmetic is definitely a top sport. Now I’m going to rest first. The moment something special comes again, I will think about whether I will make an effort or whether I will spare myself.”