Mathematics was the study of numbers.
Romulus and Remus Sylvest were mathematical geniuses. (TV: The Twin Dilemma) Peter Hutchings was a professor of mathematics at the University of Cambridge. (PROSE: Timewyrm: Revelation) Danny Pink taught mathematics at Coal Hill School. (TV: Into the Dalek)
Some of the companions of the Doctor studied or taught mathematics. Jackson Lake was a mathematics teacher. (TV: The Next Doctor) Alistair Gordon Lethbridge-Stewart taught mathematics at Brendon Public School. (TV: Mawdryn Undead) Adric was awarded a gold star badge for mathematical excellence. (TV: Full Circle) Zoe Heriot introduced herself to the Second Doctor and Jamie McCrimmon as "astrophysicist, pure mathematics major", to which her colleague, Dr Gemma Corwyn, added "with honours." (TV: The Wheel in Space)