(idiomatic) To act in one's own interests; to act in a manner advantageous primarily to oneself.

Alternative form of what's your phone number?

(mathematics) The real number system adjoined with two extra symbols: ∞ and −∞, inheriting the ordering of the real number system, and defining −∞ to be less than any real number, and ∞ to be larger than any real number.

Alternative form of look out for number one

(fandom slang, idiomatic) To remove the copyrighted elements from an existing work of fan fiction so that it may be commercially published as original fiction.

(US, law enforcement, dated) A person who ranks highest on the federal government's prioritized list of wanted criminal fugitives.

plural of Stirling number of the second kind

(mathematics) The number of ways to partition a set of n objects into k non-empty subsets, denoted by S(n,k).

(mathematics) A positive integer n which there is a positive integer e such that d(n)/nᵉ ≥ d(k)/kᵉ for all k > 1, where d(n) is defined to be the divisor function of n

(mathematics, number theory) A branch of number theory in which suitable ideas and techniques from analytic number theory are generalised and applied to a variety of mathematical fields.