Numbers can be categorized into subsets called rational and irrational numbers. An example of irrational numbers are decimals that have no end or are non-terminating. A common confusion is that because a decimal has no end it is a large number that tends to infinity, whereas that isn’t true.
Take a look at the exponential constant e, e has a value of 2.7182818… and is non-terminating but not a huge value because at the end of the day e will never be greater than 3. On the other hand, rational numbers are decimals that can be written as fractions that divide two integers (as long as the denominator is not 0). Thus, for this problem, since the square root of 2811, or 53.019, is a non-terminating decimal, so the square root of 2811 is irrational.