11 (number)

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

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 on 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 "Captain Grumpy" and "Number Ten" having used up two further regenerations in his cycle. (TV: The Time of the Doctor)