27 (number)

27 was a number.

At one point during their failure, a Kroton calculated they would have to reserve power for 27 further minutes before it exhausted. (TV: The Krotons)

Vega 3 was 27 light-years from Earth. (PROSE: K9 and the Beasts of Vega)

Through use of a magnetron, the New Dalek Empire transported 27 stolen planets from across time and space to the Medusa Cascade, where they collectively served as an engine for the Daleks' reality bomb. (TV: The Stolen Earth/Journey's End)

When arguing with Clara Oswald over who should hack Ms. Kizlet's software, the Eleventh Doctor, among other factors, listed his 27 brains as to why it should be him. When Clara expressed doubt about this, he admitted to it being an exaggeration. (TV: The Bells of Saint John)

The Twelfth Doctor identified at least 27 different species living in Trap Street. (TV: Face the Raven)

Behind the scenes
In NOTVALID: The Curse of Fatal Death, the Ninth Doctor calculates that he has saved every planet in the known universe a minimum number of 27 times.