Yellow Pig Day

We have celebrated July 17 as Yellow Pig Day since the 1960s. I’m not sure I entirely understand it myself, but here’s the scoop from Time and Date: “The unofficial holiday was created in the early 1960s by Princeton mathematics students, David Kelly and Michael Spivak, while working on the special properties of the number 17. It is unclear why the day was called Yellow Pig Day or what a yellow pig has to do with the number 17, though legend has it that it is in reference to David Kelly’s collection of yellow pigs.”

The number 17 is significant mathematically because it is not only a prime number (divisible only by itself and one); it is also the sum of the first four prime numbers, 2, 3, 5, and 7. However, what this has ultimately to do with yellow pigs is obscure, to say the least! At any rate, it is nice to have a holiday for mathematicians.

I must admit I had never heard of this holiday in spite of working for nearly twenty years on college campuses, but if the Web is to be believed, Yellow Pig Day is an important part of the academic calendar and is celebrated with cake, parades, and general revelry. There are even yellow pig carols, which you can find on There we have such songs as “March of the Yellow Pig,” sung to the tune of “The Battle Hymn of the Republic,” and “The Seventeen Days of Yellow Pigs,” based on the “Twelve Days of Christmas.” There are, of course, seventeen songs on that page.

By the way, if all the talk of pigs and numbers has made you a bit queasy, you might want to know that the fear of the number 17 is called heptadecaphobia.

Quotes about numbers and pigs

To most outsiders, modern mathematics is unknown territory. Its borders are protected by dense thickets of technical terms; its landscapes are a mass of indecipherable equations and incomprehensible concepts. Few realize that the world of modern mathematics is rich with vivid images and provocative ideas.–Ivars Peterson

If people do not believe that mathematics is simple, it is only because they do not realize how complicated life is.–John Louis von Neumann

I never did very well in math – I could never seem to persuade the teacher that I hadn’t meant my answers literally.–Calvin Trillin

Arithmetic is where numbers fly like pigeons in and out of your head.–Carl Sandburg

Mathematics is not a careful march down a well-cleared highway, but a journey into a strange wilderness, where the explorers often get lost.–W. S. Anglin

Although he may not always recognize his bondage, modern man lives under a tyranny of numbers.–Nicholas Eberstadt

I used to love mathematics for its own sake, and I still do, because it allows for no hypocrisy and no vagueness….–Stendhal

As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality.–Albert Einstein

Pure mathematics is the magician’s real wand.–Novalis

I am fond of pigs. Dogs look up to us. Cats look down on us. Pigs treat us as equals.–Winston S. Churchill

Never wrestle with pigs. You both get dirty and the pig likes it.–George Bernard Shaw

I never met a pig I didn’t like. All pigs are intelligent, emotional, and sensitive souls. They all love company. They all crave contact and comfort. Pigs have a delightful sense of mischief; most of them seem to enjoy a good joke and appreciate music. And that is something you would certainly never suspect from your relationship with a pork chop.–Sy Montgomery

The paradise of my fancy is one where pigs have wings.–G. K. Chesterton

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