7 was a prime number. (AUDIO: The Haunting)
According to Jo Grant, three sevens were equal to 21. (TV: The Claws of Axos)
7 was not divisible by 2. (PROSE: And Then Again)
Following his regeneration, the Seventh Doctor noted that he was in his "seventh persona". (TV: Time and the Rani) According to the Doctor, the Holy Number of Nirvana was 7. (COMIC: The Enlightenment of Ly-Chee the Wise)
When En-Gula was seven, her mother died and she was taken into the temple of Ishtar at Kish. (PROSE: Timewyrm: Genesys)
Gallifreyan genes constituted only 7% of Alex Campbell's genome. (AUDIO: Relative Dimensions)