9 (number)

9, or IX in Roman numerals, was a number. (AUDIO: The Odds Against)

The Ninth Doctor considered it to be his lucky number. (AUDIO: The Other Side)

The Lamadines had nine opposable digits. (TV: Terror of the Autons)

According to Jo Grant, 108 divided by 9 was 12. (TV: The Claws of Axos)