originally published February 15, 2014

What is your favorite number?

It’s an odd question, if you really stop to think about it. Why have a favorite number? Okay, maybe it’s the number that was splashed across your jersey when you played high school basketball. Perhaps you hit it big with a fortuitous spin of the roulette wheel once. Maybe you met the love of your life on a bus with that number, on the street with that number, at precisely that number o’clock, on that number’s day of the month. If so, please tell me about it; that’s a great story.

Mathematician Alex Bellos is conducting a survey to figure out what’s the most common favorite (or, I suppose, lucky) number. I entered my pick, but found myself torn. While I am a firm believer in the notion of luck, inasmuch as the universe seems to unfold in a fortuitous manner some days, I don’t cling to a specific digit. What would I pick? My daughter was born on the 26th, I met my wife in ’95, my favorite childhood football player wore 33… it all seems so arbitrary and unnecessary.

The current front-runner in Bellos’s survey is seven. This comes as no surprise; with its omnipresent visage in all forms of gambling, from seven-digit lotto games to the most dreaded and praised roll in a game of craps, seven is the smoke-choked caterpillar on life’s giant toadstool. Seven sees all, man.

Any integer housed in that exclusive neighborhood of Single-Digitsville is going to find itself wrought with significance throughout religious and secular history. But there’s a special pedestal reserved for seven. Not only has this digit turned more fortunes than any other in the hallowed halls of Vegas casinos, but it has found itself firmly entrenched within the spirit of humanity. Why do we love seven so? Maybe because it’s a prime number, mighty and indivisible. Yet seven fits into logic’s keyhole with a crooked and devilish squeak.

You can tell if a large number is divisible by five if it ends in a ‘5’ or ‘0’. You can divide it by four if the last two digits in the number are themselves a multiple of four. Add up the individual digits in this large number; if you end up with a multiple of three, you can divide the entire number by 3. But seven? There’s simply no way of knowing if a number divides neatly by seven until you try. No shortcuts, no clues. Seven is a seductive enigma.

I don’t want to get all mathy here (I did that just last week and my wife was not pleased), but there’s another weird numerical quirk in Miss Seven’s bottom drawer. If you divide 999,999 by seven, it works out to a whole number: 142,857. Those six numbers in that order make up each fraction of seven:

1/7 equals 0.142857 (and the numbers repeat infinitely). 2/7 is 0.285714. 3/7 is 0.428571, and so on. I don’t know if that’s a really common math occurrence – nor do I need to know; don’t write in – but it’s pretty cool.

The ancient Egyptians revered seven as a God number. It’s said that the goddess Isis was guarded by seven scorpions, and that the god Osiris’s body was torn into fourteen pieces: seven for Upper Egypt and seven for Lower Egypt.  The Egyptians were big on sacred numbers, and seven topped the charts.

Our little seven glyph used to look like the shepherd’s hook on the left. That was how the old-school Hindus used to write it, and that’s how it eventually caught on in the western world. The western Ghubar Arabs added the diagonal swoosh. If you’re on the European continent or in Latin America you probably add a horizontal dash through the middle of your seven – this is an effective way of differentiating it from a ‘1’. Plus, if you take the time you can make it into a little bow tie, which is fun for everyone.

Craps players know seven as the joyous bringer of mirth on a round’s initial roll, and the subsequent she-beast of money-sucking Satan if it shows up beyond that. Seven is the most common sum when a pair of dice are hurled; it’ll show up about 1/6th of the time. This is part of the reason why ‘7’ is the only symbol to appear in a standard slot machine configuration – the number has broken more hearts and/or filled more wallets than any other in the gambling world.

Seven shows up more frequently in religion than does a cliché joke in a crappy sitcom. Jesus had seven final utterances on the cross. The world was created in seven days (counting the resting/football day at the end). There are seven deadly sins and seven virtues. The Catholics observe seven sacraments. Hindus believe in seven worlds in the universe (not sure if Pluto’s demotion will affect this). Muslims believe there are seven layers of the earth, and seven levels of hell and heaven. Even in the fake world of Westeros on Game of Thrones, there are seven ancient gods and seven kingdoms. In Harry Potter: seven school years, seven horcruxes, seven Weasley kids, and so on. The number is custom-made for mysticism.

The simultaneously ethereal and tactile world of music swims deep in number seven waters also. We have seven notes in our major and minor scales, just as India has seven octats as the basis of their musical structure and traditional Persian tunes are built atop seven dastgahs. Hell, even old 45 records are seven inches in diameter. It just fits.

Seven is huge in the world of sports as well. Some of the greats from every game – Mickey Mantle, John Elway, Phil Esposito – have earned the retirement of the number seven from their teams’ rosters. In football, seven is a touchdown (plus extra point), in baseball seven is the inning in which we stretch.

Most mammals have seven cervical vertebrae. There are seven objects (counting the sun and our moon) from our solar system which can be seen by the naked eye from earth. Isaac Newton defined seven colors of the rainbow, though in all fairness I think he was just being unimaginative.

We have seven days in a week and as many as seven seasons among native peoples in certain parts of Australia or Montana – though where I live we only have two: winter and its brief respite. Just as we can dial ‘1’ for long distance here in North America, Russians will dial ‘7’. Other countries use two or three-digit codes.

I’m sure I could make a similar case for the significance of ‘6’ or ‘8’, but seven is a unique beast, worthy of its quizzical attention and temporal affections. It’s not my favorite number (right now, that honor might just go to ‘1000’), but it’s a good one.

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