Is 57 composite?

A composite number is a number expressible as the product of two numbers apart from #1# (or #-1#) and itself (or minus itself).

So in the case of #57#, we are looking for a factorisation other than the trivial #57 = 1 * 57# (or #57 = (-1) * (-57)#).

Note that #5+7 = 12# which is divisible by #3#.

So we can deduce that #57# is divisible by #3#.

In fact:

#57 = 3 * 19#

So #57# is expressible as the product of two non-trivial factors and is therefore composite.

#57 = 19 * 3#

#57# is the product of #19# and #3#.

this means that #57# can be written as the product of two numbers, neither of which are #1# (or #0#).

a composite number is a positive integer (a whole number greater than #0#) that has at least one divisor other than #1# and itself.

only composite numbers can be written as the product of two positive integers, neither of which are #1#.

as the product of #19# and #3#, #57# is composite.

#57# is a composite number because it has more factors other than #1# and #57# .

Also #57# can be uniquely expressed as a product of its Prime factors :-

#57 = 3^(1).19^1#