REBECCA ROBERTS, host: Welcome back to the 101st ALL THINGS CONSIDERED of the year. I'm Rebecca Roberts.</s>REBECCA ROBERTS, host: Let's start our exploration of All Things 101 with a look at the number itself.</s>Mr. CHRISTOPHER CALDWELL (Mathematician, University of Tennessee): A hundred and one is the 26th prime number. Prime numbers are numbers greater than one that are only divisible by themselves and one.</s>REBECCA ROBERTS, host: That's prime number guru Christopher Caldwell from the University of Tennessee. He says number groupies have developed all sorts of wacky terms for primes. For example, 101 is classified as a twin prime.</s>Mr. CHRISTOPHER CALDWELL (Mathematician, University of Tennessee): A hundred and one, 103 are - together make a pair of twin primes. Twin primes are two primes that differ by two, like three and five or 11 and 13. We believe there's infinitely many of them, but at this point, we cannot prove that's true.</s>REBECCA ROBERTS, host: One thing that is true, 101 is the first cyclops prime.</s>Mr. CHRISTOPHER CALDWELL (Mathematician, University of Tennessee): Well, a cyclops prime is one with a zero in the middle of it. So a single zero in the middle of number kind of like having an eye in the middle.
April 11 is the 101st day of the year. Mathematician Christopher Caldwell explains some of the mathematical mysteries surrounding the number. For instance, 101 is a "cyclops prime" — a prime number with an "eye" — or zero — in the middle.