Both
'proper' methods start with the lowest prime that divides into the
value, and uses that until it won't go. Then we use the next prime that
divides and so on.
Example: Find the product of the prime factors of 280
2 into 280 goes 140 and so on
35 is odd so doesn't divide by 2
3 does not divide exactly into 35 so we use 5
So the answer is 2x2x2x5x7 [or 23x5x7]