In my book The Strong Delusion under what is going to happen conjecture I said that 666 could represent body, soul, spirit. Notice that just as the descendants of the Fallen Angels are eternally condemned, so are those who receive the mark of the beast in the tribulation period, they have NO FORGIVENESS and are eternally condemned to the lake of fire with the devil and his angels : Rev 14:9 And the third angel followed them, saying with a loud voice, If any man worship the beast and his image, and receive his mark in his forehead, or in his hand, Rev 14:10 The same shall drink of the wine of the wrath of God, which is poured out without mixture into the cup of his indignation; and he shall be tormented with fire and brimstone in the presence of the holy angels, and in the presence of the Lamb: Rev 14:11 And the smoke of their torment ascendeth up for ever and ever: and they have no rest day nor night, who worship the beast and his image, and whosoever receiveth the mark of his name.