24 was a number.

There were twenty-four hours in an Earth day. (TV: The Moonbase, Last of the Time Lords)

A night on Darillium lasted twenty-four years. (TV: The Husbands of River Song)

When the Twelfth Doctor asked Clara Oswald to pick a two-digit number, she chose 24. He then asked the crew of the crew to look at the first word of page 24 of the book they were holding, as part of the Helman-Ziegler test. (TV: Last Christmas)

Of the twenty-seven planets stolen from across time and space by the New Dalek Empire, twenty-four of them were taken in the year 2009. (TV: The Stolen Earth/Journey's End)

Raphael was twenty-four when he met the Seventh Doctor and Ace. (PROSE: Timewyrm: Apocalypse)

Chronon, (WC: 14682 UNIT Field Log, 14683 UNIT Field Log, 14684 UNIT Field Log) or cronon (WC: 14681 UNIT Field Log) and artron energy readings during the recording of UNIT field logs included 17%, (WC: 14682 UNIT Field Log) 18%, 19%, (WC: 14681 UNIT Field Log, 14682 UNIT Field Log) 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, (WC: 14682 UNIT Field Log) 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, (WC: 14682 UNIT Field Log, 14684 UNIT Field Log) 90%, (WC: 14682 UNIT Field Log, 14683 UNIT Field Log) 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, 101%, 102%, 103%, 104%, 105%, 106%, and, in the case of Chronon energy, 107%. (WC: 14683 UNIT Field Log)