"666 is the occult number of the Hexagram, the symbol of the Sun, for a single line of the Hexagram contains three equal parts, each of which may be represented by the number 1, so that every line can be symbolized by the number 111. There are six lines in all, so that 111x6=666, the most Holy Number of the Sun. Each angle of the Hexagram is 60 degrees. 60 is the number of the Hebrew letter Samekh, which is the letter of the Holy Guardian Angel or the Solar Self in Man. Six angles of 60 degrees each equals 360 degrees, and 360 is the number of the Hebrew letter Shin spelled in full. Shin is the letter of the Sun and of 666. Also 666 is the number of a "Man" who lives in the Sun." (David Cherubim, aka, Frater Aurora Aureae of The Order of the Thelemic Golden Dawn, a Qabalistic secret society, as quoted in his work Thelmic Numbers and Words, http://thelemicgoldendawn.net/documents/hexagram.htm

"The Six-Pointed Star or Hexagram, is called the Tetragrammaton and is the symbolic representation of the Jewish-Talmudic G-d of the Kabbala. The Sephirotic Tree of the Cabala taught that the sum of the numerical values of Ain-Soph (166, absolute empty) and Kether (500, unity) gives 666, i.e., the Sun.)" ( source: see Ask The Rabbi)

This calls for wisdom. If anyone has insight, let him calculate the number of the beast, for it is man's number. His number is 666. (NIV) Rev 13:18