Find the least number that must be subtracted from 980 so as to get a perfect square. Also, find the square root of the perfect number obtained.

Find the smallest and the greatest 4-digit numbers, each of which is a perfect square.

The product of two numbers is 256. If one number is four times the other, find the numbers.

The area of a square plot is 2116 m². A man takes 5 rounds of the boundary of this plot, find the distance covered by him.