what is the prime factorization of 7020?

Start by dividing out a 2:  7020  =  2 x 3510

Since the answer is even, divide out another 2:  7020  =  2 x 2 x 1755

Since the sum of the digits of 1755 is 1 + 7 + 5 + 5 = 18 is divisible by 3, so is 1755:

    7020  =  2 x 2 x 3 x 585

Since the sum of the digits of 585 is 5 + 8 + 5 = 18 is divisible by 3, so is 585:

    7020  =  2 x 2 x 3 x 3 x 195

Since the sum of the digits of 195 is 1 + 9 + 5 = 15 is divisible by 3, so is 195:

    7020  =  2 x 2 x 3 x 3 x 65

65 is not divisiible by 3, but it is divisible by 5:

    7020  =  2 x 2 x 3 x 3 x 3 x 5 x 13