Permutable Prime

Two silly chickens, giggling and spinning a wooden top on my kitchen floor.

Two silly chickens, giggling and spinning a wooden top on my kitchen floor.


Hank: (pajamas, teeth washed, face brushed) Mama, how was your birthday? Was it the best?

Me: It was my best birthday, thank you very much. I wouldn’t have wanted anything more.

Hank: Except not stale cake.

Me: That’s what happens when all the tables are occupied at Pastelaria (bakery) Fina. (sigh, whispering) You and I can go to Fina after lunch and have a nice slice of cake to erase the memory of that cake completely tomorrow.

Hank: Okay! That’s right. I am on ferias (vacation). I don’t go to school until Quinta-Feira (thrusday).

Me: Lucky boy.

Hank: Carnival is not as good as Halloween…

Me: Less candy.

Hank: But more ferias (vacation)!

Me: (giggling) Truth.

Hank: Whatcha looking at?

Me: I am reading about permutable prime numbers.

Hank: What are those?

Me: “A permutable prime, also known as anagrammatic prime, is a prime number which, in a given base, can have its digits’ positions switched through any permutation and still be a prime number.”

Hank: Um… I only understood some of that.

Me: Do you know what a prime number is?

Hank: Um…

Me: A prime number can only be divided by 1 or it’s self.

Hank: OH yah.

Me: Such as 23, 5, 7, 11, 13, 17, 19, 23, 29, 31 annnnnnnnnnnnnd 37.



Hank: That’s interesting.

Me: Did you hear that last number?

Hank: um, no I stopped listening.

Me: 37.

Hank: You’re 37. Today. You’re 37 today.

Me: I am and a friend of mine sent me this birthday message, “Happy birthday! My gift to you: 37 is the 12th prime number and is “permutable” because 73 is also prime (which is the 21st prime).”

Hank: Who sent you this? Leslie Blaha? She’s a math scientist!

Me: True, but no. Another friend, Winter, he is also a scientist. He visited us for a day when we lived in Setúbal with Liz and Rob and Gabe.

Hank: The walkie-talkies in the car day?

Me: The very one.

Hank: I am sorry for Winter because all I remember from that day was driving through the Serra de Arrábia and taking to someone with the walkie-talkies.

Me: That someone was Winter. Your papa played the tour guide and Winter repeated the stories and local facts to your car following behind ours through the walkie-talkies.

Hank: Ohhhhhh-kay!

Me: SO going back to the permutable prime numbers…

Hank: Yes, please.

Me: You know I don’t speak or read Math very well at all. I am hardly fluent.

Hank: No you speak fairy tale and adventure and imagination.

Me: (smiling, nodding) Well, here I was thinking turning 37 was no big deal. I am glad I’ve had 36 trips around the sun and I’m excited to start my 37th tour, but 35 and 40 those ages feel more important making 37 feel rather ordinary. Now Winter has shown me that 37 is a uniquely special age since it is a permutable prime number. It is a prime number forward and backward: 37 and 73. 37 is a prime palindrome. Permutable prime numbers are fun and extraordinary and the next time I will be a permutable prime number again will be on my 71st birthday and the last time I turned a permutable prime was on my 31st birthday, but I had no idea what a permutable prime was then so I missed my opportunity to enjoy it.

Hank: WHOA, 71? That is like forever away.

Me: Forever is sooner than you think, my dove.

Hank: When was the last time I was a permutable prime.

Me: According to the list it was when you were 7, but the first time you will be a double digit permutable prime will be on your 11th birthday and the first time you will be a triple digit permutable prime number will be your 113th birthday.

Hank: Cooooooool.