Today, March 14th, is known as Pi Day among nerds in the United States, namely because 3.14 are the first three digits of the famed number, π. As you probably remember from math class, pi represents the ratio of a perfect circle’s circumference to its diameter.

Here are a few facts you might not know about this crazy number:

**1. It’s impossible to represent pi as a fraction.**

Pi is an irrational number, which means it’s impossible to represent as a ratio between two non-integer numbers. Two thousand years ago, Archimedes gave it a shot and found that π was somewhere between 220/70 and 224/71.

**2. Pi Day also happens to be Albert Einstein’s birthday.**

In Princeton, New Jersey, Einstein’s hometown, *Pi Day* takes on special significance. The town hosts numerous events throughout the week to celebrate mathematics’ most famous man and number.

**3. The mirror image of 3.14 is “PIE.”**

**4. The American government only recently recognized Pi Day.**

“Pi Day” was the birthchild of physicist Larry Shaw, who organized the first Pi Day celebration at the San Francisco Exploratorium in 1988. It wasn’t until over twenty years later, on March 11, 2009, that the U.S. House of Representatives passed a resolution proclaiming March 14 to be National Pi Day.

**5. Some people think Pi Day should be celebrated on July 22.**

In Europe, Pi *Approximation *Day is celebrated on July 22, because much of the world would write today’s date as 14/3. Many argue that 22/7 is a closer approximation to pi anyway.