1000000000000000 (number)

1000000000000000 was a number.

According to the War Doctor, a combined force of "a billion billion" Daleks attacked Gallifrey on the last day of the Last Great Time War. As a result of the first thirteen incarnations of the Doctor transporting Gallifrey to a pocket universe, the vast majority of the Daleks were destroyed when the planet vanished, causing them to inadvertently fire upon each other in its absence. (TV: The Day of the Doctor)

According to Kenossium, all Matrix prophecies concurred that the Hybrid would destroy a billion billion hearts to heal its own. (TV: Hell Bent)