28 (number)

28 was, according to Eugene Jones, a perfect number: equal to the sum of its dividers. (TV: Random Shoes)

Revna was 28 when the Seventh Doctor visited Kirith. (PROSE: Timewyrm: Apocalypse)

The Ninth Doctor spent 28 years waiting on Earth to meet up with Rose in 1922. (AUDIO: The Other Side)