OK, So I'm helping hit Jnr with his homework and this has me stumped!

We need a text that describes a number and used the same amount of characters (no numbers, spaces, symbols or punctuation). So:

8 = TWOCUBED

10 = SIXADDFOUR

20=FOURMULTIPLIEDBYFIVE

We have worked out all of them from 8 to 20 apart from the number 9! It's driving us nuts! Can anyone come up with one?