Given a,n∈N, the additive order of a modulo n is, equivalently:
The
order of
a in the
group (Z/n,+)
The value
LCM(a,n)/a; that is, the
least common multiple of
a and
n divided by
a
The
minimal ℓ∈N such that
ℓ timesa+a+⋯+a is divisible by
n
The
minimal ℓ∈N such that
ℓ⋅a≡0 (mod n)