I think 666 has to do with day of the week you worship God.
66.6 = 2/3
Zechariah Chapter 13
8And it shall come to pass, that in all the land, saith the LORD, two parts therein shall be cut off and die; but the third shall be left therein.
9 And I will bring the third part through the fire, and will refine them as silver is refined, and will try them as gold is tried: they shall call on my name, and I will hear them: I will say, It is my people: and they shall say, The LORD is my God.
(Will they be calling on 666?)