The number above the symbol is the atomic mass (or atomic weight). This is the total number of protons and neutrons in an atom. The number below the symbol is the atomic number and this reflects the number of protons in the nucleus of each element's atom. Every element has a unique atomic number.
According to enstiens theory of relativity, c is constant in E=mc^2 c is the speed of light. and many other physicsts all calculate it to be the same amount, <span>299,792, 458 meters per second. </span>