Numbers: The Good, the Bad, and the Ugly


Happy Friday the 13th! Although those of you with triskaidekaphobia (and especially paraskevidekatriaphobia) probably aren’t so thrilled about today.   So how lon ghas it been considered unlucky?  According to Snopes, some anonymous person stated “Now Friday came, you old wives say, Of all the week’s the unluckiest day” back in 1656, which is why it took more than 300 years for the phrase TGIF to catch on.  On the other hand, written records of Friday the 13th as an unlucky day are only about 100 years old, appearing in 1913 in Notes & Queries (I can’t find detail on which issue) and also in a news article from1908, although that focuses primarily on the bad luck of the number 13 itself.

But even if the date bothers you, consider yourself lucky: 2008 has only one Friday the Thirteenth. Next year there will be three (in February, March, and November).

13 isn’t the only unlucky number. The number 666 is disliked by many christians, and not all that long ago its appearance in Social Security Cards led to the rule that, if a person objects to the digits of their Social Security number for religious or cultural reasons, then they can request a new number.

The number 4 is unlucky in both Chinese and Japanese culture, because the word for 4 () sounds like the word for death; as a result, the word for 14 sounds like accident or Will Die, and 514 sounds like You Will Die. Bummer of a hotel room.

On the other hand, 6, 8, and 9 are lucky numbers in Chinese culture: the word for 6 (liù) can also mean flowing or smooth. 8 means prosperity, fortune, or wealth, which is why this year’s Olympics in Beijing will start at 8pm on 08/08/08. The word for 9 (jiŭ) can also mean long-lasting (and wine!), so 9 is associated with a long life. And 7 is often viewed as a lucky number in the United States (and probably elsewhere). This site has more info about numbers in Chinese culture, and this site even more about numerical superstitions in general.

So we have good numbers and bad numbers, but what about ugly ones? To my surprise, a few sites on the internet define an ugly number as a number whose only prime divisors are 2, 3, or 5. But here I must claim that Beauty in in the eye of the beholder: those are the exactly the numbers whose reciprocals have finite decimal (well, sexagesimal) expansion in Ancient Babylonian’s Base 60 writings. And with that “I can’t believe I just thought of that on a Friday afternoon” tidbit, I’ll leave you to enjoy the rest of the day!

The photo above is of an elevator in a hotel in Buenos Aires. It was taken by a user of the b612 blog and licensed under Creative Commons Attribution ShareAlike 2.0.

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