15 (number)

15 was a number.

The Archangel Network was composed of fifteen satellites orbiting the Earth. (TV: The Sound of Drums/Last of the Time Lords)

When the Cybermen attempting to capture the moonbase first detected the relief ship from Earth, their computer predicted it would land on the lunar surface in fifteen minutes. (TV: The Moonbase)

The interior of the Doctor's TARDIS decreased in size by fifteen centimetres following the Doctor's regeneration into his second incarnation. (PROSE: Invasion of the Cat-People)