Topic summary
Multiplicative order
In number theory, given a positive integer n and an integeracoprime to n, the multiplicative order of a modulo n is the smallest positive integer k such that a ≡ 1 (mod n).
In other words, the multiplicative order of a modulo n is the order of a in the multiplicative group of the units in the ring of the integers modulon.
The order of a modulo n is sometimes written as ordn(a).