Twenty-seven is a multiple of nine.
I learned my nines by watching Square One on PBS. There was some annoying country and western song that taught that, when dealing with a two-digit number, the number is a multiple of nine if you add the two digits together and you get nine. Thus, 27. 2+7=9. 3x9=27. Get it? Other multiples of nine = 18, 36, 45, 54, 63, 72, and 81. And 90, of course.
Anywho, that's how I learned my multiples of nine, and to this day any time I see one of the numbers above, I think about that dag-blasted country song from Square One. (All I really remember about it is that the chorus featured a whiny sounding lady singing "Nine, nine, nine!", but I suppose it did its job)
Update: My sister informs me that, in the state of Kansas at least, they no longer teach students to memorize their multiplication tables. What the crap???