A number used to contact a particular fax machine.

(mathematics) A positive integer which is divisible by the sum of all of its digits.

(mathematics, number theory) A branch of number theory that uses methods from mathematical analysis to solve problems about the integers.

(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.

(number theory) The subfield of number theory concerning the behaviour of sumsets (integer sets added to each other elementwise).

Synonym of basic reproduction number

(number theory) An integer which is one more than two raised to a power which is itself a power of two (i.e., is expressible in the form 2^(2ⁿ)+1 for some n>0); equivalently, a number that is one more than two raised to some power (is expressible as 2ⁿ+1) and is prime.

(mathematics) A positive even integer that can be expressed as the sum of two odd primes; involved in Goldbach's conjecture.

(Jamaica, slang) To engage in anal sex; to bugger; to sodomize.

(optics) A dimensionless quantity (denoted F), such that for an electromagnetic wave passing through an aperture and hitting a screen, F=(a²)/(L𝜆) where a is the characteristic size (e.g. radius) of the aperture, L is the distance of the screen from the aperture, and 𝜆 is the incident wavelength.