The Bible's answer
According to the last book in the Bible, 666 is the number, or name, of the wild beast with seven heads and ten horns that comes out of the sea.(Revelation 13:1, 17, 18)
This beast is a symbol of the worldwide political system, which rules over "every tribe and people and tongue and nation"- -(Revelation 13:7)
The name 666 identifies the political system as a gross failure in God's sight. How?
More than a label. Names given by God have meaning. For example, God gave the man Abram, which means "Father Is High (Exalted), the name Abraham, which means "Father of a Crowd (Multitude)" when God promised that He would make Abraham "'a father of many nations." -(Genesis 17:5, footnotes) Likewise, God named the beast 666 as a symbol of its defining attributes.-(Genesis 17:5, footnotes)