Raise a Glass to Mathematics on Yellow Pig Day

It’s the early 1960’s. We're at a bar across the street and we overhear two Princeton mathematics students deliberating over drinks. “This yellow pig has 17 toes, 17 teeth...” says one. The other exclaimed, “...and 17 eyelashes!”

Fast forward to present day. Every July 17th there is now a “National Yellow Pig Day,” which commemorates the unique attributes of the prime number 17. Mathematicians all over celebrate the occasion with Yellow Pig carols (yes, songs), cake, and showing off how much they know about the prime number.

How in the world did this all transpire, you ask? Well, this unique holiday was originated in the early 1960’s by Princeton mathematicians, Michael Spivak and David C. Kelly, who were feverishly analyzing the unique properties of the number 17 for an assignment. After intense rounds of brain gymnastics (and probably a few pints), they thought up the peculiar yellow pig with 17 toes, 17 teeth, 17 eyelashes, and so on. They decided that there should be a day that celebrated it, and July 17th was going to be the day!

Did You Know?

Remember the Number Creatures segment on Sesame Street?

17 is the only known prime that is equal to the sum of digits of its cube (173 = 4913 and 4 + 9 + 1 + 3 = 17)

Since becoming drinking buddies at Princeton, Spivak and Kelly went on to have illustrious careers in mathematics. Spivak, who received the Leroy P. Steele Prize in 1985, is an author of several well-known mathematics books, most of which are rumored to have hidden references to the Yellow Pig. Kelly founded the Hampshire College Summer Studies in Mathematics (HCSSiM) in 1971, where he was a professor emeritus of mathematics. To this day, HCSSiM celebrates this annual holiday “where joy, humor, and interestingness take the place of formulas, drills, and multiple-choice tests.”

Does the number 17 have any significance in your experiences so far? Or, have you spotted the Yellow Pig in one of Spivak’s books? Let us know in the comments below.