数字 (Sūji, numbers) have a special place in the Japanese language that’s not all about 機能 (kinō, functionality), 数学 (sūgaku, math) or 測定 (sokutei, measurement).

In spite of their precise nature, numbers have always been allotted a lot of wiggle room, specifically when it comes to ダジャレ (dajare, puns) category.

For example, take the calendar. The 29th of every month has been deemed 肉の日 (Niku no Hi, Day of Meat), because of the 2(ni, two) and 9 (ku, nine). Get it? Nine can be read ku or kyū. Some people hold 肉の日 パーティー (Niku no Hi Pātii, Meat Day Parties) for a legitimate excuse to binge on barbecue and roasts. Sept. 1 is キウイの日 (Kiui no Hi, Day of the Kiwi) to match the Japanese pronunciation of the New Zealand fruit and 9-1 (kyūi). And so it goes.

ちなみに (chinami ni, by the way), many older Japanese count from one to 10, not as “ichi, ni, san …” but “hi, fu, mi, yo, itsu, mutsu, nana, yatsu, kokonotsu, tō.” Nov. 22 is いい夫婦の日 (Ii Fūfu no Hi, Happy Husband and Wife Day), because of the repetition of one (ichi abbreviated to i,) followed by a pair of twos read fu. The recently retired shogi player Hifumi Kato’s kanji for his first name is 一二三, which at first glance looks like a code.

Other names with numbers are more like puzzles. There are more than a few people with their last name written with the single character of 一 (ichi, one). This is read out loud as にのまえ (Ninomae) meaning, “the one before two.” My grandmother claimed to know a girl of that surname with the first name of Miyako — and her kanji name was written out like this: 一 三八子. Apparently, the girl wasn’t born on March 8, but her parents wanted the number 8 because it symbolizes prosperity and looks like Mount Fuji, smack in the middle of their daughter’s name. The 三 (mi or san, three) was because she was the third child.

Or how about 四月一日? Read normally, it’s Shigatsu Tsuitachi, which is April 1. In the old days, the first of April was traditionally when people took cotton padding out of their garments, in deference to the official arrival of warm weather. So anyone with this rare surname is “Watanuki,” meaning “to take out the cotton.”

Other numerical puns are simpler: 4649 is よろしく (yoroshiku, nice to meet you, or otherwise a formal greeting) — each number standing for each hiragana; and 5963 is ごくろうさん (gokurōsan, thanks for your trouble), though these feel a little outdated today.

Before the advent of smartphones, 184, いやよ (iyayo, no way), was often used by young women in text messages to ward off unwanted invitations from men, but whom they also wanted to avoid rejecting outright. Interestingly, 184 was also the number you’d push to conceal caller identity.

Used like that, Western numbers can be fun, but the 漢数字 (kansūji, numbers written out in kanji) are another story. Often having roots in Buddhism, the kansūji are difficult to write, read and comprehend.

Take 那由多 (Nayuta) for example. Originally taken from the Sanskrit word meaning “a very large number,” one nayuta is generally acknowledged as 10 to the power of 60, though some people argue that it’s to the power of 72. The unit after nayuta is called 不可思議 (fukashigi, deeply strange) and there are various views on how many digits this number may have. The word is more commonly used for its meaning of strangeness than as a number.

Even without going that far, kansūji can be quite complex, though phonetically, they are the same. In the old way, 一 is written as 壱, 二 is 弐, 三 is 参, 五 (go, five) is 伍, 十 (, 10) is 拾 and 百 (hyaku, 100) is 佰. When preparing a 香典袋 (kōdenbukuro, bereavement or funeral money) or 祝儀袋 (shūgibukuro, congratulatory money), it’s customary to write the cash sum on the envelope in kansūji.

Interestingly, the number 十三 (jūsan, 13) doesn’t have the same ominous tone as it does in the West. Rather, it often has positive connotations.

十三夜 (Jūsanya, the 13th moon) is thought to be just the right night for お月見 (otsukimi, moon-watching). It’s also the title of a famed short story by Ichiyo Higuchi, whose portrait adorns the ¥5,000 bill, and was later adapted into part of an omnibus film 「にごりえ」 (“An Inlet of Muddy Water”) in 1953 by Tadashi Imai. In the lunar calendar, the 13th moon is Sept. 13, and Japanese traditionally observed this night by turning out the lights, eating sweets and watching the moon.

Jūsan can also be pronounced “Jūzo” and was a fairly common boy’s name. The late actor and filmmaker Juzo Itami once told me a love for numbers ran in his family. His filmmaker father’s real name was Yoshitoyo Ikeuchi but he chose 伊丹万作 (Itami Mansaku) as his pen name because he loved the kanji 万 (man, 10,000). His son Yoshihiro took up the name 十三 “because it sounded poetic.”

Writing out numbers in kanji with a calligraphy brush is one of the first lessons taught in お習字 (o-shūji, calligraphy) classes in grade school and it’s harder than you think. They say getting the right balance in a simple kanji like 二 and 三 teaches you some valuable life truths. One can only hope some of them stuck.

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