What: The number 13. Here, 30 seconds in, is the late Elliott Smith performing my favorite Big Star song, “Thirteen,” which of course makes it my favorite Elliott Smith song:

Why: Thirteen is the number that leaves childhood behind. You learn quickly to count to 10 on your fingers, and rapidly jump up to 12 through counting months and ladybugs and Christmas gifts of birds and people. But 13 represents some sort of maturity for counting, the point past which The Count stops counting and Schoolhouse Rock aliens run out of toes. Thirteen’s a number for serious things: for colonies, for Last Supper participants, for letters in many serial killers’ names. In a literal sense, 13 represents the age of maturity, past which you will be expected to make your own damn decisions. It’s the age when you can go to high school, when you can choose whether or not to have a bar mitzvah (I picked “not”). It’s when the doors of superhero blockbusters open up to you, and no one questions if you can have that rap album. Thirteen is when you become real.

Impact: No positive integer demands and gets the respect that 13 does, due to its ageless association with unluckiness. There is no phobia named quadrophobia, but triskaidekaphobia is a life-altering problem for millions. If the 13th falls on a Friday, millions of Americans won’t get on airplanes. Many of those airplanes don’t have 13th rows, many buildings don’t have 13th floors. Microsoft has no Office version 13, Hammurabi’s Code has no 13th law, Formula One has no #13 cars. It is also the title of the absolutely, positively scariest movie of all time.

Personal Connection: Thirteen years ago to this day, Evon and I coordinated six lighting changes, one movable stage, five colored ribbons yoking our shoulders, and one awesome wedding. That’s a very lucky 13. Happy anniversary, honey.

Other Contenders: the highly rational irrational number pi, which I once analyzed to the 7500th digit for an MIT puzzle; 10, the perfect number for a list or a short film on relative distances that believes there’s a place called “Soldiers Field”; the Eye of Horus, the Egyptian representation of 1 broken into its component fractions; a googolplex, a number coined by a 9-year-old to define “1, followed by writing zeroes until you get tired”; 667, the neighbor of the beast.