Having or bearing an even number.

the number of particles per unit volume

(mathematics) Any integer which is the product of some integer with the integer itself.

(number theory) The branch of number theory that deals with transcendental numbers.

(mathematics) A positive integer that is divisible by every one of its digits.

(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

a phone number (on a phone call) that is unfamiliar to the recipient / a hidden number; a phone number that is hidden from the recipient

(geometry) The maximum number of layers of copies of the same shape that can surround a given shape.

(UK, telecommunications, historical) A telephone number consisting purely of digits, introduced in the 1960s to replace numbers that began with an alphabetic code for the exchange.

(epidemiology) The expected number of infection cases to be directly infected by an infected individual, given a population that is equally susceptible.