(number theory) Any natural number greater than 1 that cannot be formed by multiplying two smaller natural numbers.

A number used to denote quantity; a counting number; a cardinal. / (mathematics) A generalized kind of number used to denote the size of a set, including infinite sets.

(grammar) A word that expresses the relative position of an item in a sequence. / (arithmetic) A natural number used to denote position in a sequence.

(mathematics) A number that can be expressed as the ratio of two integers.

(number theory) A number that is less than the sum of its proper divisors (all divisors except the number itself).

A telephone number not listed in the directory.

plural of atomic number

plural of decimal number

(algebra, field theory) algebraic number field

(genetics) The number of copies of a gene or plasmid within a cell's genome. / (library science) The identification number assigned to a specific copy of a work.