78 (number)

78 was a number.

Margaret Waterfield was seventy-eight years old at the time of her death on 16 April 1909. (PROSE: Birthright)

According to the Twelfth Doctor's sonic sunglasses during the Monk invasion of 2017, Nardole had a resting heart rate of 78BPM. (TV: The Pyramid at the End of the World)