11 (number)

11 was a prime number. (AUDIO: The Haunting)

The Doctor's universe had 11 dimensions in all, (PROSE: Parasite) including three "primary dimensions" of space, (TV: Flatline, AUDIO: The Invasion of E-Space, Paradise Five) and either two dimensions of time, (PROSE: The Quantum Archangel) or time and space as the fourth and fifth dimensions. (TV: "An Unearthly Child") The remaining planes formed the Six-Fold-Realm. (PROSE: The Quantum Archangel)

The Eleventh Doctor's room in the prison ship hotel, which contained his greater fear, was number 11. (TV: The God Complex)

He considered himself to be in his eleventh incarnation, (TV: The Lodger, The Name of the Doctor) despite technically having used up all twelve regenerations afforded to him. At the end of this incarnation, the Eleventh Doctor affirmed that he was "Number Eleven", despite the existence of "Captain Grumpy", his actual ninth incarnation and his previous self who he called "Number Ten" having used up two further regenerations in his cycle. (TV: The Time of the Doctor)

The Twelfth Doctor once told Bill that "eleven plus two" was an anagram of "twelve plus one", to which Bill responded that both of these were equal to 13. (COMIC: Harvest of the Daleks)