I have read that neutron stars weigh thousands of tons per cubic cm. I wanted to verify this. I assumed the neutrons are spheres and basically touch each other with a packing factor of 65%. I divided the mass of a neutron by its volume and multiplied by 0.65 (the packing factor). Unless I made an error, the result is BILLIONS of tons per cubic cm, not thousands. So what is the spacing of neutrons in neutron stars, and what keeps them separated at this spacing?