The Heads of the Beast - Arethmos Gar Antarpu

In the ancient world, the letters of the alphabet doubled for numbers. Aleph was one, Bait was two, Gamal was three and so forth. Nero Caesar in Hebrew or Aramaic is typically spelled neuron cassar. The N in Nero has a value of 50 in the Hebrew Aramaic numbering system. So you add all that up and neuron cassar becomes 666.