# Are non-base-10 numbers ever written in kanji?

This morning I was thinking about the joke "There are only 10 types of people in the world: those who understand binary, and those who don't". Considering if this would translate well to Japanese, I figured it would have to use `十` to represent the 10. But `十` represents the actual value of 10, not just the digits '1' and '0' juxtaposed. However, if you wrote it as just `一〇` (or possibly `一零`), it (almost) completely ruins the joke.

So does Japanese mathematics even write numeric notation using kanji? If so, how are radices greater than 10 handled? Because traditionally, the symbols used are letters, starting with A=10, B=11, and so on. Presumably Japan had mathematicians long before encountering (Latin?) letters, so how did they represent the >10 values?

Realize this may be too localized and not generally helpful. Close if necessary.

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The prices in restaurants are often written in kanji, in decimal notation: 一三八〇円, where zero is written not 0, but 〇 (which should appear when converting maru in most IMEs). – Earthliŋ Mar 13 '13 at 16:21
This is only sort of relevant, but you might be interested in reading about 算木 and 十干. I've read that the latter is still used sometimes the way we'd use A, B, C (甲・乙・丙). – snailboat Mar 13 '13 at 16:54
@snailplane: Ha, I actually made a topic about 十干. Didn't even cross my mind. `sawa`'s answer there talks about applications in mathematics. – istrasci Mar 13 '13 at 17:01
この世には10種類の人間しかいない。二進数を理解する人間と理解しない人間だ。 Link: ja.wikipedia.org/wiki/… – Dono Mar 14 '13 at 0:42
Someday somewhere on a forum "Are non-base-10 numbers ever written in full letters? Would english-speaking people get the joke if we write it `there are only ten types of people...`"... – oldergod Mar 14 '13 at 4:11

A distinction is usually made between positional numeral systems and non-positional.

Let's use Arabic numerals as an example of a positional numeral system. In this kind of system, if we write 100, each digit represents a coefficient in an exponential series. Let's use b to represent the base:

1b2 + 0b1 + 0b0 = 100

Okay, so what about 漢数字? The numbers 一, 十, and 百 each consist of one numeral and each represent different powers of ten, but they do so without respect to position. So in this use of 漢数字, we say they're non-positional. In this system, it makes the most sense to say 十 represents the value ten. It doesn't represent an exponential series like the one above because there's no correspondence between position and degree.

Notice how in the example of Arabic numerals above, I didn't specify a base. It might be decimal, or it might be binary. You can't say the same for 一, 十, and 百. With the numbers represented by these numerals, there is no meaningful definition of b, so it doesn't make sense to talk about what base the numbers are written in.

However, there is a positional use of 漢数字, as well. 漢数字 supplanted 算木 as a positional numeral system in Japan after the 16th Century, and in modern Japan both positional and non-positional uses exist. For example, user1205935 wrote in a comment that a restaurant price may be written `一三八〇円`. This number is clearly written using positional numerals:

b3 + b2 + b1 + b0 = 一三八〇

We've demonstrated that a base exists! We haven't demonstrated what base it is, and that's the crux of your question. In this case, it's obvious the base is 10. But is it always?

I can't prove it, but I've searched and looked through history books, and I can't find any evidence that it's ever not 10. It seems like there's a very strong preference for Arabic numerals when writing numbers in any base but ten. In fact, I found people joking about what the numeral sequence would be if it did continue, implying it doesn't. (Someone suggested 十土王圭, which I include here for humor value.) So, in the absence of evidence to the contrary, I conclude that the answer is:

No, kanji is not ever used to write values in bases other than decimal.

Two historical notes:

1. The historical Chinese numeral 十 was once written as a vertical line, and this old form was combined with 一, 二, 三　and the old form of 四 to form single numerals representing the values 11-14. See here and here on Wikipedia. However, I believe these forms had passed out of use before kanji was adopted in Japan.

2. According to Wikipedia, in the old non-positional system, the juxtaposition 二八 represented the value 16 (二×八） rather than 28. I believe this sort of use is still around to some extent in, for example, 四六時中, which represents 四×六 through juxtaposition.

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I realize this isn't a great answer, but I decided to post it anyway in case it was helpful! – snailboat Mar 14 '13 at 7:48
About your first historical note, it seems like they're still used in Cantonese: 廿/卄, 卅 and 卌 – 小太郎 Mar 26 '13 at 4:33

Japanese people use the Arabic numerals "10" too. They would get the joke if you just write "10".

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Yes, I'm aware of that, but getting the joke across isn't the point of my question. – istrasci Mar 13 '13 at 17:04

Numbers written in kanji are analogous in English to numbers written out in full. The joke would be just as ruined in English if it were written "There are only ten types of people..."

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