As long as it’s spherically symmetric (which it is, near enough), you can treat it as a point from anywhere outside. So the distance from which it would exert a field of 1/2 g would be sqrt(2) times the Earth’s actual radius.
As long as it’s spherically symmetric (which it is, near enough), you can treat it as a point from anywhere outside. So the distance from which it would exert a field of 1/2 g would be sqrt(2) times the Earth’s actual radius.