2.8×10^39 picometers is circumference of the observable part of our universe, roughly. A sole hydrogen atom has a bohr radius of about 25 picometers.
So 40 digits of pi would indeed be in the ballpark for computing anything distance-wise at the circumference of the observable universe down to the hydrogen electron cloud size.
One of the siblings posted a link from JPL about the number of digits they use for their highest precision calculations. In that article they also state that 37 decimals would be sufficient for calculating the cirumference of the observable universe down to the accuracy of the diameter of a hydrogen atom.[0]
