“At this point many of his disciples turned away and deserted him” (John 6:66 NLT).

THE “666” OF JOHN’S GOSPEL
In John 6:66, the shocking statement that Jesus made concerning His body and blood as spiritual food, made many so-called disciples desert Him. Just as Moses had led a “mixed multitude” (Ex. 12:38) into the wilderness from Egypt, so a mixed multitude followed Jesus. On this day in the synagogue in Capernaum, Jesus separated those who only followed for the free bread, from those who followed because they truly believed.
 
In John’s Revelation, he wrote of another “666” (Rev. 13:16-18), the mark of the beast, which in the last days will cause many to turn away from God and turn to the Antichrist, in order to buy bread. Those who receive this mark will come under the “wrath of God” (Rev. 14:9-11), for they will have rejected the Bread of Life in order to eat the temporal bread of this world.
 
I suppose there are many “666” moments when those who follow Jesus must count the cost. In those moments, true believers will continue to follow Jesus no matter the cost. But false believers will turn away and desert Him.