a prime number is a number which is only divisible by itself and one e.g 2, 3 , 5, 7when writing a number (in this example 36) as a "product of its prime factors" you need to find the prime numbers which you need to multiply together to get 36. you do this by using a factor tree. when using a factor tree you divide the original number by prime factors until you reach a number which is also a prime factor. In this example 36 divided by 2 is 18. divide that by 2 is 9 divine that by 3 is 3. so 36 as a product of its prime factors is 2x2x3x3