The area is not sufficient information to determine the length and width. First of all, there is no reason to suppose that the area is rectangular as opposed to circular or triangular or some other simple or complicated shape.

5 acres is 217,800 square feet. The smallest perimeter for 5 acres will be attained if it is a circular area with a perimeter of 1654.37 ft.

Or the 217,800 square feet could be in the form of a rectangle which is:

467 ft * 467 ft (approx) and a perimeter of 1,867 ft or

2,178 ft * 100 ft and a perimeter of 4,556 ft or

21,780 ft * 10 ft and a perimeter of 43,580 ft or

2,178,000,000 ft * 0.0001 ft and a perimeter of 4,356,000,000.0002 ft
As you can see there is no upper limit.