07700 900461 was a telephone number used by the Doctor, each time on two distinct handsets.
In the 21st century, the Sub-Wave Network contacted the Tenth Doctor on this number, reaching the phone Martha Jones had previously given to him. (TV: The Stolen Earth [+]Russell T Davies, Doctor Who series 4 (BBC One, 2008).)
McGillop of UNIT recognised 07700 900461 as a number associated with the Doctor when the Eleventh Doctor called him, although this time the Doctor used the phone that was connected to the exterior of his TARDIS. (TV: The Day of the Doctor [+]Steven Moffat, 50th Anniversary Specials (BBC One, 2013).)
It was later changed to 95475949. (COMIC: The Swords of Kali [+]Robbie Morrison, Doctor Who: The Twelfth Doctor (Titan Comics, 2014-2015).)