This question also has an answer here (in German):
Was für ein Geschlecht hat eine Zahl?
In my textbook I noticed that one of the characters uses feminine gender when pointing at a number written somewhere, precisely what he says is "Das ist eine 8". I know from Google etc. that letters are strictly neutral (as in "Das ist ein B"), but I've not found any clue on how to distinguish genders for a digit. In Russian, though, we associate almost every number with feminine, the only exceptions are zero and numbers of big magnitude like 1 million, 1 billion etc., which are masculine.
So for German, do you also have most of them as feminine so I can follow my "Russian intuition" for them, or are there drastically different rules, or even maybe every speaker decides themselves?