plural of Wratten number

Any of the arbitrary alphanumeric codes in a system for labelling optical filters, usually for photographic use.

(mathematics) Relating to number theory

plural of student number

A code assigned to a student upon entering an educational institution, and used to identify the student in official documents.

(mathematics) A positive integer that cannot be expressed as the sum of all the proper divisors of any positive integer (including the untouchable number itself).

plural of untouchable number

plural of copy number

(astronomy) The total number of stars in the observable universe, often estimated to be in the sextillions.

(number theory) An odd natural number k such that k⨯2ⁿ+1 is composite for all natural numbers n.