Since man was created on the sixth day (Gen. Gen. 1:26-27), six is considered to be the number of man. The repetition of the number thrice in association with the number of the Beast is understood to denote the trinity of man or satanic trinity (Satan, the Beast, and the false prophet). Six is the number of man, who was created on the sixth day. In Revelation Rev. 13:18+ it represents the number of the ultimate man, the Antichrist: 666.2
The number six seems to denote specifically the will and independence of man (i.e., sin) as evidenced by the mention of the number of fingers and toes of men who were notably powerful in their defiance of God (2S. 2S. 21:20; 1Chr. 1Chr. 20:6).3
Six also denotes incompleteness, being one less than seven, the number of completeness or perfection. The Menorah has one central stem out of which six stems branch (Ex. Ex. 25:32-33). Some see this as an indication of mans incompleteness (the six branches) made complete only with the addition of Messiah (the central branch). As Jesus said, John 15:5) In the same way that six days of work are incomplete without the seventh day of rest, mans utmost effort when independent of God results in incompleteness and failure.
Six days were appointed to him for his labour; while one day is associated in sovereignty with the Lord God, as His rest. Six, therefore, is the number of labour also, of mans labour as apart and distinct from Gods rest. . . . the number is significant of secular completeness.4In the book of Revelation is presented the final great effort of the human secular system to achieve its ends apart from God. The cataclysmic events in response to the unbridled will of man are Gods ultimate reminder of mans innate inability and deficiency apart from God, which the earth-dwellers refuse to acknowledge to the bitter end.
Among the enemies of God marked by the number six: we find Goliath, whose height was six cubits, having six pieces of armor and a spears head weighing six hundred shekels of iron (1S. 1S. 17:4-7); Nebuchadnezzar, whose image was sixty cubits high and six cubits wide (Dan. Dan. 3:1); and Antichrist, whose number is six hundred and sixty-six (Rev. Rev. 13:18+). Even Solomon at the height of his earthly glory received a mere six hundred and sixty-six talents of gold (1K. 1K. 10:14) each year and sat on a throne of only six steps (1K. 1K. 10:19). Solomon, in his advanced human wisdom, great power and influence, but eventual drift from God, illustrates characteristics shared by the Antichrist of the end.
Throughout history, the best that man can produce by every available means and effort of rebellious will is 666 which falls short of Gods triune completeness (777).
3 The great giant had six fingers on each hand, and six toes on each foot, for he represented the perfect example of that race of giants.Walter L. Wilson, A Dictionary of Bible Types (Peabody, MA: Hendrickson Publishers, 1999), 374.
4 E. W. Bullinger, Number in Scripture: Its Supernatural Design and Spiritual Significance (Grand Rapids, MI: Kregel Publications, 1967), 150.