Your answer would be total number of atoms! This is because when you have these equations which require total number of atoms.
Place the magnet at one end of the piece of metal. The magnet must make as much contact with the metal as possible. Place light pressure on the magnet and rub the metal in one direction only. Magnetization will take some time to accomplish so continue rubbing until the iron or steel attracts other pieces of metal.
"The proton and neutron have nothing to do with the isotope little billy"