Show me how you calculated that.
1sq mile = 5280ftx5280ft = 27878400ft sq
27878400ft sq x 147042 miles sq (sq miles in montana) = 4.099295...x10^12 ft sq
4.099295...x10^12/2500 = 1,639,718,277 units
so yeah, not saying it's your fault though because it's a commonly said phrase