The cototient of a positive number n is defined as n - ϕ(n), where n is the totient function. It is therefore the number of positive integers <=n that have at least one prime factor in common with n. The first few cototients for n = 1, 2, ... are 0, 1, 1, 2, 1, 4, 1, 4, 3, 6, 1, 8, 1, 8, 7, ... (OEIS A051953).

highly cototient number | totient function