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);

Seems like you’re trying to fit 20-digit value into a float, so it cuts along the way. Try using double