Style guides are always fascinating. I wish I could forget about them, but various clients have different ideas about how they want English to be written, and on top of that I used to teach English grammar, which meant laying down some laws. Here's the UK Government digital style guide: Government Digital Service Content principles This is weird:
2.17 Numbers Write all numbers in numerics (including 1 to 9) except where it’s part of a common expression and it would look strange, eg ‘one or two of them’. Use common sense. ‘One of the 13 words in this sentence is causing problems: this 1.’ This sentence would be better with ‘one’ as the final word.
My rule would have been to write 'thirteen', and indeed to write all numbers up to ninety-nine in words (German often says to write from one to twelve in words, but even there I am constantly encountering '1.' ('first') in the middle of quite serious and non-abbreviated texts). Of course the problem then arises, as it did for me recently in a translation about genetics, that when you are discussing statistics you should write all numbers as figures. But then there comes a bit of text where it's no longer about statistics ...Zum vollständigen Artikel