Newton's Law of Gravitation states that the gravitational force between any two objects is the product of their masses divided by the distance between their centres of mass squared all multiplied by the gravitational constant.
there fore F = (Gm1m2)
Gravitational constant = 6.67x10^-11 , F = 1 and m1 and m2 = 2
apply in above formula we get 1 = (6.67x10^-11 x 2 x 2)/r^2
rearranging, we get r^2 = 6.67x10^-11 x 2 x 2
therefore r^2 = 2.6692x10^-10 therefore r = 1.634x10^-5 m