Realistic gravity much too strong

I'm creating a game with realistic gravity and orbital mechanics, but when I plug in numbers for the mass of the planet, the gravity created is much much stronger than it realistically should be. I believe there is some kind of unit conversion error, but I can't figure out what that would be. Thanks for any help you guys could provide.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Gravity : MonoBehaviour
 {
 
     public GameObject planet;
     public GameObject ship;
 
     private Vector3 planetPosition;
     private Vector3 shipPosition;
 
     public Rigidbody shipRigidbody;
 
     private float shipMass = 2000.0f;
     private float planetMass = 86700000000000000000.0f;
 
     Vector3 startVelocity = new Vector3(0f, 0f, 0f);
 
 
 
     //Newtons Gravity Equation
     public Vector3 calculateForce()
     {
         //Find the positions of the objects
         planetPosition = planet.transform.position;
         shipPosition = ship.transform.position;
         //Distance between the objects (r)
         float distance = Vector3.Distance(planetPosition, shipPosition);
         //Distance squared (r^2)
         float distanceSquared = distance * distance;
         //Gravitational Constant (G)
         float G = 6.67f * Mathf.Pow(10, -11);
         //F = G*m*m / r^2
         float force = G * ((planetMass * shipMass) / (distanceSquared));
         //Get the heading
         Vector3 heading = (planetPosition - shipPosition).normalized;
         //Turn the force from just a value into a 3D vector with direction
         Vector3 forceWithDirection = (force * (heading/heading.magnitude));
         //Return Force
         return (forceWithDirection);
     }
 
     void Start()
     {
         //Give Ship initial velocity
         shipRigidbody.AddForce(startVelocity, ForceMode.VelocityChange);
     }
 
     // Update is called once per frame
     void FixedUpdate()
     {
         //Calculate and add the force of gravity to the ship
         shipRigidbody.AddForce(calculateForce() * 0.1f, ForceMode.Impulse);
     }
 }