Editing Divisibility rule (section)

===Composite divisors===
A number is divisible by a given divisor if it is divisible by the highest power of each of its [[prime number|prime]] factors.  For example, to determine divisibility by 36, check divisibility by 4 and by 9.<ref name="product-of-coprimes"/>  Note that checking 3 and 12, or 2 and 18, would not be sufficient.  A [[table of prime factors]] may be useful.

A [[Composite number|composite]] divisor may also have a rule formed using the same procedure as for a prime divisor, given below, with the caveat that the manipulations involved may not introduce any factor which is present in the divisor.  For instance, one cannot make a rule for 14 that involves multiplying the equation by 7.  This is not an issue for prime divisors because they have no smaller factors.