Integer square root

In number theory, the integer square root (isqrt) of a non-negative integer n is the non-negative integer m which is the greatest integer less than or equal to the square root of n, $${\displaystyle \operatorname {isqrt} (n)=\lfloor {\sqrt {n}}\rfloor .}$$

For example, ${\displaystyle \operatorname {isqrt} (27)=\lfloor {\sqrt {27}}\rfloor =\lfloor 5.19615242270663...\rfloor =5.}$