23 was a number.
While observing a rocket from the Wheel, Tanya Lernov read readings so that Zoe Heriot could carry out a mental calculation. The lineal reading was 198.42 metres at 23 degrees latitude and 190.03 metres at 24 degrees latitude. (TV: The Wheel in Space)
Abslom Daak was sentenced to Exile D-K after being found guilty of "23 charges of murder, pillage, piracy, massacre and other crimes too horrible to bring to public attention." He was told the life expectancy of a Dalek Killer was 2 hours, 32 minutes and 23 seconds. (COMIC: Abslom Daak... Dalek Killer)