A number is between 17 and 22. It has prime factors of 2 , and 5. What is the number?

The number would be 20 because these are factors of 2 ... 2,4,6,8,10,12,14,16,18,20 and factors of 5 ... 5,10,15,20 they both are factors of 20. So your answer would be 20. Just to make sure ... let's try 17 well it can't be a factor of 2 because it's an odd number and we couldn't do 18 because it's not a factor of 5. We can't do 19 because it's not a factor of 2 or 5. 20 is a factor of both. 21 isn't a factor of 2 or 5. Lastly we have 22 ... well it's a factor of 2 but not a factor of 5.