## Why we All Love Numbers

### We cannot help but react to numbers, but why are odds masculine and evens feminine? Why were Levi's 501s and WD-40 given those names? And is number 3 really 'warm' and 'friendly'? Alex Bellos does the maths

Jerry Newport asks me to pick a four-digit number.

“2761,” I say. “That’s 11 x 251,” he replies, reciting the numbers in one continuous, unhesitant flow. “2762. That’s 2 x 1381. 2763. That’s 3 x 3 x 307. 2764. That’s 2 x 2 x 691.”

Jerry is a retired taxi driver from Tucson, Arizona, who has Asperger syndrome. He has a ruddy complexion and small blue eyes, his large forehead sliced by a diagonal comb of dark-blond hair. He likes birds as well as numbers, and when we meet he is wearing a flowery red shirt with a parrot on it. We are sitting in his living room, together with a cockatoo, a dove, three parakeets and two cockatiels, which were listening to, and occasionally repeating, our conversation.

As soon as Jerry sees a big number, he divides it up into prime numbers. This habit made his former job driving cabs particularly enjoyable, since there was always a number on the licence plate in front of him. When he lived in Santa Monica, where licence numbers were four and five digits long, he would often visit the four-storey car park of his local mall and not leave until he had worked through every plate. In Tucson, however, car numbers are only three digits long. He barely glances at them now. “If the number is more than four digits I’ll start to pay attention to it. If it’s four digits or less, it’s roadkill. It is!” he remonstrates. “Come on! Show me something new!”

Asperger’s is a psychological disorder in which social awkwardness can coexist with extreme abilities, such as, in Jerry’s case, an extraordinary talent for mental arithmetic. In 2010, he competed at the Mental Calculation World Cup in Germany having done no preparation. He won the overall title of most versatile calculator, the only contestant to score full marks in the category where 19 five-digit numbers have to be decomposed into their constituent primes in 10 minutes. No one else even got close.

Jerry’s system for breaking down large numbers is to sieve out the prime numbers in ascending order, extracting a 2 if the number is even, extracting a 3 if it divides by three, a 5 if it divides by five and so on. He raises his voice to a yell: “Oh yeah, we’re sievin’, baby! Yeah! Jerry and the sievers!”

His wife, Mary, who is sitting on the sofa next to us, a musician and former Star Trek extra, also has Asperger’s, which is much less common in women than it is in men. A marriage between two people with Asperger’s is rare, and their unconventional romance was turned into the 2005 Hollywood film Mozart and the Whale.

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