1020 is divisible by the prime number 2 which results in 510. The same step can be applied 1 more time and the resultant value will be 255. Continuing, the number 255 is divisible by prime number 3 and the result after division will be 85. Continuing, the number 85 is divisible by prime number 5 and the result after division will be 17. The result 17 cannot be divided any further as it is a prime number. Hence the prime factors of 1020 are 2, 2, 3, 5, 17.

1020 is divisible by the prime number 2 which results in 510. The same step can be applied 1 more time and the resultant value will be 255. Continuing, the number 255 is divisible by prime number 3 and the result after division will be 85. Continuing, the number 85 is divisible by prime number 5 and the result after division will be 17. The result 17 cannot be divided any further as it is a prime number. Hence the prime factors of 1020 are 2, 2, 3, 5, 17.