Learn more fun facts on the Yellow Pig Day Video Page.
- Categories:
- Special Interest
- Tags:
- Appreciation
- Where:
- United States
- Date change rule:
- Every July 17
- Holiday emoji:
- 🔢
Yellow Pig Day lights up the calendar every July 17, inviting math enthusiasts and curious minds alike to explore the fascinating properties of the number 17. Dive into its quirky history, discover mind-boggling facts, and find super-smart suggestions to make this day a fun celebration of mathematics.
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Expected Yellow Pig Day Deals
While Yellow Pig Day isn’t a major retail holiday, look for niche promotions from educational retailers and online stores. In past years, brands like ThinkFun and MindWare have offered discounts on math-related games and puzzles. Online learning platforms such as Khan Academy might feature special content or challenges related to the number 17. Independent bookstores and specialty toy stores could also highlight books on number theory or mathematical curiosities. We will update this page with confirmed live deals as July 17 approaches.
Platform Guide for Yellow Pig Day
Tag @nationaltoday_ and use #YellowPigDay. Share photos of your favorite math puzzles, quirky pig art, or creative ways you’re celebrating the number 17.
TikTok
Tag @www.nationaltoday.com and use #YellowPigDay. Film short videos explaining a fun math fact about 17, showcasing a math trick, or participating in a numerical challenge.
X/Twitter
Mention @NatlToday and use #YellowPigDay. Tweet out interesting facts about the number 17, engage in math riddles, or share your favorite mathematical paradoxes.
Yellow Pig Day Hero
Michael Spivak
History of Yellow Pig Day
In the 1960s, students Michael Spivak and David Kelly were studying math at Princeton. Together, they spent a lot of time considering the qualities of the number 17 and became obsessed with its incredible combination of simplicity and complexity that was recurrent in the mathematics they were using and developing.
Their obsession grew into a desire to celebrate the number 17 with its own special day, and they created a mascot for their event in the form of a yellow pig. But they morphed their pig into a beast with 17 teeth, 17 toes — 17 everything! — to encapsulate their passion for the number 17.
From its small beginnings, Yellow Pig Day has become a huge hit in the academic calendar, with students and teachers alike coming together to celebrate this special number, as well as math in general. Classes sing yellow pig carols, share cake, and play games based around the number 17. Some people even create origami yellow pigs and yellow pig T-shirts to wear with pride.
Both of its founders still work in the field of mathematics. Kelly continues to be involved in the organization of the holiday each year, commemorating the day with food, songs, and a reunion. His obsession with the number 17 is still going strong, and he even gives a special lecture on the subject every summer. He founded the Hampshire College Summer Studies in Mathematics (HCSSiM), a six-week program for mathematically talented high school students, designed to inspire and encourage them in the general field of mathematics, though it also probably includes the number 17 somewhere!
Yellow Pig Day timeline
Yellow Pig Day founders Michael Spivak and David Kelly are born.
Michael Spivak and David Kelly create Yellow Pig Day following their obsession with the number 17.
David Kelly founds the Hampshire College Summer Studies in Mathematics (HCSSiM).
The carol ‘The March of the Yellow Pig’ is composed to commemorate the day and is still sung on college campuses in celebration.
How Businesses Can Celebrate Yellow Pig Day
Local businesses can embrace Yellow Pig Day by hosting math-themed trivia nights or puzzle challenges, especially at cafes or game stores. Bookstores can create displays featuring books on number theory, mathematical history, or quirky science facts. Tutoring centers might offer special workshops or discounts on courses related to the number 17, encouraging a deeper appreciation for mathematics among students.
Yellow Pig Day FAQs
When is Yellow Pig Day?
Yellow Pig Day 2026 falls on Friday, July 17, a perfect mid-summer opportunity to delve into the fascinating world of numbers. This fixed date ensures a consistent annual celebration of mathematics.
What is special about the number 17?
The number 17 is a prime number, meaning it’s only divisible by 1 and itself. It’s also the seventh prime number. In mathematics, 17 holds several unique properties, including being a Fermat prime and appearing in various mathematical puzzles and theorems.
How popular is Yellow Pig Day?
Yellow Pig Day is a niche but beloved observance, primarily celebrated within academic circles, particularly among mathematicians and students. Its popularity is concentrated among those who appreciate quirky mathematical traditions and intellectual humor.
What is the origin of Yellow Pig Day?
Yellow Pig Day originated in the 1960s at Hampshire College, created by mathematicians Michael Spivak and David C. Kelly. It began as an inside joke and a way to celebrate the number 17 through a complex, whimsical mathematical system involving yellow pigs with 17 eyelashes.
Yellow Pig Day Activities
Collect 17 things
Celebrate the number 17 by collecting 17 things from your favorite category — flowers, books, chocolates, the choice is yours!
Draw a yellow pig
Create your own Yellow Pig Day mascot for the day, and make sure to include the number 17 somehow for extra credit!
Research the number 17
The number 17 has some fascinating properties, as well as a resonance throughout history. You’ll be surprised by what you find!
5 Intriguing Facts About The Number 17
It’s a prime number
As a prime number, it’s a number that is greater than 1 that cannot be formed by multiplying two smaller numbers.
It’s the sum of the first four prime numbers
If you add the first four prime numbers together (2+3+5+7) you’ll get the number 17. That’s one of the things Yellow Pig Day founders loved so much about it!
It’s democratic
The 17th Amendment of the United States Constitution grants citizens the right to a democratic vote on their chosen senators.
It’s a sporting record
In 1993 the Pittsburgh Penguins achieved the longest winning streak in NHL history with 17 wins.
It’s poetic
The popular poetic form, the haiku, is structured using 17 syllables, in three lines of 5, 7, and 5 syllables.
Why We Love Yellow Pig Day
Math is useful!
From simple arithmetic to complex algebra, we use math in our everyday lives, often without even realizing it.
It makes math fun
When things get complicated, it can be easy to switch off from math. But Yellow Pig Day reminds us that math can be fun and informative — a winning combination!
It’s an excuse to geek out
When you’re passionate about something, you can make it exciting for other people, just like Yellow Pig Day founders did with the number 17. What things can you geek out on to inspire others?
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