4 (number)

4 was a number.

According to Jo Grant, three sevens times four were equal to 84. Also according to her, 12 divided by 4 was 3. (TV: The Claws of Axos)

Some species, like the Empathivores, (COMIC: The Whispering Gallery) the Moxolon Swamp Vipers, (TV: The Vault of Secrets) the Tractites (PROSE: Genocide) and the Tetraps (TV: Time and the Rani) had four eyes.

Vulpana had four moons. (AUDIO: The Moons of Vulpana)

The Fifth Doctor told the First Doctor that he was on his fourth regeneration. (TV: The Five Doctors)

To his recollection, Elton Pope saw the Tenth Doctor on the night of his mother's death when he was "three or four" years old. (TV: Love & Monsters)

Before the Genesis Ark opened, the Doctor believed that the Cult of Skaro were the last four Daleks in existence. (TV: Doomsday)

The countdown towards the Ninth Doctor's eviction on Big Brother counted from 6 to 0, going through 5, 4, 3, 2, and 1. (TV: Bad Wolf) In an emergency transmission sent by the TARDIS, the Thirteenth Doctor listed 5 things that she did in any worrying situation. The fourth was listening to science and doctors. (WC: Message from the Doctor)