Let a divisor  of 
 be called a 1-ary (or unitary) divisor if 
 (i.e., 
 is relatively prime to
 
). Then 
 is called a 
-ary divisor of 
, written 
, if the greatest
 common 
-ary
 divisor of 
 and 
 is 1 (Cohen 1990).
In this notation, 
 is written 
,
 and 
 is written 
.
 is an infinitary
 divisor of 
 (with 
)
 if 
.
Suryanarayana (1968) unfortunately uses a different and conflicting definition.