What is the length and width of 871000 square feet?

There is no reason to assume that 871000 sq feet are in the form of a rectangle. That area could be a circle, a triangle or any other shape.

Even if it were a rectangle, the area is not sufficient information to determine its linear dimensions.

Suppose L is any number greater than sqrt(871000) feet = 933.27 ft (approx)

and let W = 871000/L feet.

Then a rectangle with dimensions L ft x W ft will have an area of L*871000/L = 871000 square feet. L can have ANY value greater than 933.27 feet so there are infinitely many possible rectangles.