Asks the interlocutor to give their phone number for subsequent communication.

(nautical, idiomatic) To die, to perish.

A telephone number for which an extra charge is assessed to the caller, part of which is returned to the owner of the number.

(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

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

(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