How to write 13 in Roman Numerals (Unicode)?

I know the answer seems trivial but believe me, it is not! In Unicode There are different characters for Roman numerals. For example, one is not `i` but `ⅰ` which is a different character; or a better example, two is not `ii` (that is a string of two characters juxtaposed) but `ⅱ` (that is a single character).

Here are the roman numerals for `1`, `2`, `3`, `4`, `5`, `6`, `7`, `8`, `9`, `10`, `11`, `12`, `50`, `100`, `500`, and `1,000` respectively: `Ⅰ`, `Ⅱ`, `Ⅲ`, `Ⅳ`, `Ⅴ`, `Ⅵ`, `Ⅶ`, `Ⅷ`, `Ⅸ`, `Ⅹ`, `Ⅺ`, `Ⅻ`, `Ⅼ`, `Ⅽ`, `Ⅾ`, `Ⅿ` (non-capitalized: `ⅰ`, `ⅱ`, `ⅲ`, `ⅳ`, `ⅴ`, `ⅵ`, `ⅶ`, `ⅷ`, `ⅸ`, `ⅹ`, `ⅺ`, `ⅻ`, `ⅼ`, `ⅽ`, `ⅾ`, `ⅿ`). But the question is how to construct the numerals not present in this series (`13` is just an example).

One way to write `13` is `ⅹⅲ` that juxtaposes `ⅹ` and `ⅲ` (13=10+3) and another way is `ⅻⅰ` that juxtaposing `ⅻ` and `ⅰ` (13=12+1). If the base of roman numeric system is `12`, then the latter makes more sense.

• The Roman numeric sytstem is definitely not base 12, but I wonder if the particular set, if there really is no XIII, is for clocks, who need squished up letters. There's no real reason not to just use regular Latin letters for Roman numerals (and I don't know why Unicode decided to adopt different but identical letters for them).
– cmw
Commented Apr 2, 2023 at 14:44
• In the last paragraph, you repeat `x` and `iii` twice. Should the second one probably be `xii` and `i`? Commented Apr 3, 2023 at 8:20
• This question would be improved if the question title included "unicode", e.g: "How to write 13 in Roman Numerals using unicode?" Commented Apr 3, 2023 at 10:48
• @ToivoSäwén Feel free to suggest an edit! For simple things like adding a crucial bit of information in the title, don't worry about stepping on anyone's toes. Commented Apr 3, 2023 at 12:32
• Related question on Graphic Design: Why should I ever use Unicode’s special characters for Roman numerals? Commented Apr 5, 2023 at 15:02

• The engine could be a bit "smarter" and read "thirteen" but for example when it arrives in `XI` maybe it is just the Chinese president in uppercase or it could be eleven. Commented Apr 2, 2023 at 16:03