In number theory, the Lambda function is a function on positive integers which gives the exponent of the multiplicative group modulo that integer.
The value of λ on a prime power is:
- if is an odd prime.
The value of λ on a general integer n with prime factorisation
The value of λ(n) always divides the value of Euler's totient function φ(n): they are equal if and only if n has a primitive root.