If anyone has insight, let him calculate the number of the beast, for it is man's number. His number is 666. His bottom line is six hundred sixty six. Mind, insight, or attitude could be used. I chose the most flexible.
Mind suggests both the discernment and the inclination to discern.
It might be used of a number as such, but seems to me usually to refer to the sum or total of a series or the final solution of a problem. It's the final answer, the bottom line, if you will. This beast or animal was specifically a viper, but you see how the word can be used. The bottom line for the animal is a human being marked by the image of the animal, unmarked by the image of God. The only hope for rescue is concerted education in creation principles.