Numerically, that is 3.1415926535… and so on forever without repeating.
(See the illustration above. No matter how big a circle is, it's circumference will always be 3.141592 etc. times its diameter.)
March 14 is celebrated as Pi Day by mathematicians around the world because today is 3-14 in numerical notation. Imagine what the celebration was like in 1592.
(Actually, the symbol wasn't used for this famous ratio until 1706, but the ratio itself -- or a close approximation -- has been known for more than 4,000 years. For more, see the history of pi.)
You are a mathematician if you find the following joke funny: "Pies aren't square, they're round!"
If you didn't find that funny -- or didn't even get it -- but are still reading, you have a good chance of being OtherWise.
Who else would have enough curiosity to want to know what gets a mathematician's juices flowing?