Pi Day, celebrated each year on March 14, marks our collective love for the mysterious mathematical constant—and also fine baked goods.

For Pi Day 2019, food establishments across the U.S. are celebrating with deals on apple pies and pizza pies, even chicken pot pies, all in the name of 3.141592653589793238462643383279. Yes, that is pi to the 30th decimal place, and yes, you should be impressed.

But there’s a lot more to Pi Day—not coincidentally celebrated on 3/14—than the food. So, while you’re enjoying the pie of your choice today, here are some pi basics to remember.

1. Pi represents the ratio of a circle’s circumference to its diameter. No matter how big or small the circle is, the ratio never changes. It will always be the same.

2. Pi is irrational, meaning its decimal representation is infinite and its exact value cannot be determined.

3. The never-ending number has been recognized for thousands of years, dating back to the Babylonians.

4. People have attempted to break records calculating and memorizing it. In 1975, pi was calculated to a million digits. Modern technology and algorithms now let us calculate pi into the trillions.

5. Rajveer Meena of India holds the Guinness world record for the most digits of pi memorized after reciting 70,000 decimal places of the ratio in 2015. It took him 10 hours and he wore a blindfold the entire time.

Think you can do better? Apply here.

6. Many Egyptians believe that the pyramids of Giza, one the seven wonders of the world, were built on the principles of pi, with the height of the pyramids having the same relationship with the perimeter of their base.

7. There is a language, called Pilish, based on pi. The numbers of letters of each word in a sentence match the digits. For example, this poem by Joseph Shipley published in 1960. The first word “but” has three letters, the second word “a” has one, the third word “time” has four and so on: 3.14…

8. Theoretical physicist Albert Einstein was born on Pi Day—March 14, 1879, in Germany.

9. Theoretical physicist Stephen Hawking died on Pi Day—March 14, 2018, in England.

10. Pi is the most recognized mathematical constant around the world. It is also often referenced in popular culture, including in Carl Sagan’s novel Contact.

So, there you have it—pie is great.

But so is pi.