I read an article today about the Golden State Warriors getting their 73rd win, and the properties that make the number 73 interesting (Golden State and the Mathematical Magic of Seventy-Three). Apparently there are quire a few of them! It is the 21st prime number, the number of books in the Catholic Bible... and the list goes on. One of the things mentioned about 73 that jumped out at me was that it is the "sixth emirp". What's that you say? You've never heard of an emirp? Well neither had I.
Emirp is "prime" spelled backwards. As you might guess, it is a prime number that, if you reverse the digits, you get another number that is also prime. This is restricted to non-palindromic base 10 numbers. The first few are 13, 17, 31, 37, 71, 73, 79, 97, 107, 113, etc. (OEIS A006567). Note that the primes 2, 3, 5, 7, 11, 101, 131, etc. are excluded because they are palindromic.
When sharing this with the kids over dinner, G, our precocious 3 year old, had to go potty. I offered to help. She said, "No, I can do it myself. You should stay and finish talking about numbers."
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