**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*) Spending time in 1138 Essex, the Twelfth Doctor mentioned he'd provided the citizens with "top-notch maths tuition in a fun but relevant way", among other things. (TV: *The Magician's Apprentice*) Before becoming a Renegade, the Master taught mathematics and computer science at the Prydonian Academy for a time. (PROSE: *CIA File Extracts*)

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*)

In mathematics, *i* was an imaginary number that was the value of the square root of negative one. (AUDIO: *Iterations of I*)

51 was a pentagonal number. (TV: *The Tsuranga Conundrum*)

Any number that "reduce[d] to 1 when you take the sum of the square of its digits, and continue[d] iterating it until it yield[ed] 1," was a happy number. (TV: *42*)

## Types of mathematics

An application of mathematics known as Block Transfer Computation could be used to create objects and alter spacetime. (TV: *Logopolis*)

The Tenth Doctor mentioned recreational mathematics, which involved the study of happy prime numbers, numbers which are both happy and prime. He seemed surprised it wasn't a regularly studied course. (TV: *42*)