How do you abbreviate 12 million?

Answer 1

There does not appear to be a universally accepted abbreviation for a million. Some may use "m" or "M" and others "mm" or "MM" (seems to be a financial based usage), whilst it is possible that mil. may also be used. My advice would be, in order to avoid confusion, unless you are certain that your audience will understand your abbreviation, it is best to use the full word.

Of course, mathematically speaking, you could write 12 million as 1.2 * 107 (that is to write the number in standard form) if this is what you actually meant, but this isn't really that much of an abbreviation (9 keystrokes required [including spaces naturally] compared to 10).