As in Revelation 13:10, the Greek does not have the word “calls for.” As the NASB translates, the Greek simply says, “Here is wisdom.” The passage does not intend to lay an obligation (“calls for”) upon the reader to find wisdom, or a warning that if you are not wise you will not be able to comprehend the name of the beast or its number (let alone the meaning of the name or number). It says instead that “wisdom” is “here.”
We might picture Wisdom as personified, as Solomon does in Proverbs 8:1–11. Wisdom stands on the intersections of life to instruct the people of the streets about what is really going on in all the hustle and bustle of daily activities. That is, God exposes how the dragon goes about seeking to destroy the seed of the woman (Revelation 12:17) by using not just the first beast but also the second, the twisting of truth in daily conversation. So people (just as in Proverbs 8:1–36) are called to calculate, figure out for themselves on the basis of what God/Wisdom has revealed, where and how the second beast is twisting truth to advance the agenda of the first beast and the dragon.
18 This calls for wisdom: let the one who has understanding calculate the number of the beast, for it is the number of a man, and his number is 666.