1000000000000 was a number.
The Ninth Doctor claimed that a Dalek could calculate "a thousand billion" lock combinations in a single second. (TV: Dalek [+]Robert Shearman, adapted from Jubilee (Robert Shearman), Doctor Who series 1 (BBC One, 2005).)
The Tenth Doctor detected "a million million" life forms in the Library, despite no one else being present. (TV: Silence in the Library [+]Steven Moffat, Doctor Who series 4 (BBC One, 2008).)