TITLE: Notation for multiple of a number?
QUESTION [6 upvotes]: I've have a question about the notation for a multiple of a number, I know you can write it several ways: $2|4, 4 = 2n $ where $n$ is an integer, etc, but what about this one
$$4 = \dot 2$$
I've been told that that's the correct way to put it but I've been searching for such notation on the internet and I haven't found anything similar. Is this the correct way to put it or is there another one more clear and useful?

REPLY [8 votes]: The cleanest is $2\,|\,4$, though in application it's probably most often written as a congruence
$$4\equiv 0 \pmod2\,.$$
On the other hand, $\dot 2$ rather denotes the infinte series of digits $2222...$, and is used in decimal fraction format, e.g.:
$$2/9=0.\dot2\,.$$