Let a divisor d of n be called a 1-ary (or unitary) divisor if 
(i.e., d is relatively prime to 
). Then d is called a k-ary divisor of n, written 
,
-ary divisor of d and 
is 1 (Cohen 1990).
In this notation, 
is written 
,
is written 
.
is an infinitary divisor of 
(with y > 0) if 
.
Suryanarayana (1968) unfortunately uses a different and conflicting definition.
Biunitary Divisor, Divisor, Greatest Common Divisor, Infinitary Divisor, Unitary Divisor
Cohen, G. L. "On an Integer's Infinitary Divisors." Math. Comput. 54, 395-411, 1990.
Guy, R. K. Unsolved Problems in Number Theory, 2nd ed. New York: Springer-Verlag, p. 54, 1994.
Suryanarayana, D. "The Number of k-ary Divisors of an Integer." Monatschr. Math. 72, 445-450, 1968.