What two intergers does 21 square root fall between?

List out the perfect squares: 1, 4, 9, 16, 25, ... We see that 21 is between 16 and 25. So the square root of 21 is between 4 and 5 because 4^2 = 16 and 5^2 = 25

Answer: between 4 and 5

On a calculator, you can compute sqrt (21) to get 4.58 approximately which is a value between 4 and 5