I looked at the clock just now; it was 3:43 PM. 343, I said to myself. 7 x 7 x 7 is 343. But, I continued, the time 3:43 does not refer to the number three hundred and forty-three, because the first 3 means 3 x 60, not 3 x100. 3 x 60 minutes past noon or midnight, plus 43 more minutes. 3:43 on the clock means 223 minutes past noon or midnight, past noon in this case.
Then I said to myself, wait -- is 223 a prime number? And I soon discovered that it was, because it not evenly divisible by any of the primes 2, 3, 5, 7, 11, or 13, and the square of the next-highest prime, 17, is higher than 223. It is 289.
It took me about 10 seconds to do that math in my head, and to double- and triple-check my math, and to be certain that 223 is a prime number. Without a calculator, without pencil and paper. Not Rain Man. But above average.
This is an example of why I got frustrated with people who couldn't do the math back in March 2016, when Obama, Rachael Maddow and I told them that Hillary had clinched the nomination.
Also, I am autistic, and for 9 1/2 years I haven't been able to explain to a single person how it was that Barack, Rachel and I knew. I assume Barack and Rachel have both been able to explain it to at least a few people, because they both have far more people paying attention to them, and also because neither one of them is autistic: they're both much better at talking to people, at persuading people.
Dover Books on Mathematics, at Amazon: https://amzn.to/40CvBwT
