unitary divisor

Given the divisors $d_i$ of an integer $n$, if it is the case that for a particular $d_i$ the equality $\gcd (d_i,\frac{n}{d_i})=1$ holds true, then $d_i$ is called a unitary divisor of $n$. For example, the unitary divisors of 120 are 1, 3, 5, 8, 15, 24, 40, 120 (while 2, 4, 6, 10, 12, 20, 30, 60 are proper divisors but not unitary divisors). All the divisors of squarefree numbers are also unitary divisors.