Yes, this number merits careful study. Regardless of its specific use in the Apocalypse of St John the Divine, and in the First Book of Kings (where the Queen of Sheba has to pay a tribute to Solomon of 666 pieces of gold - a reference to 666 that seems to attract very little attention strangely), it has some very special qualities. One of these is that it is the sum total of the numbers from 1 to 36 that would be used to fill up the magical square of 6*6. In other words, 1 + 2 +3 … + 36 = 666. With the number 6 being linked to both the Sun, through that luminary's placing at the centre of the Tree of Life, and to the cube, which has six sides, we should definitely be aware that the number 666 has some very powerful resonances. Worth exploring further.
PS Although there are many Hebrew nouns and phrases that have the numeric value of 666, there are only two verbs: one means 'to conceal', the other 'to profit'. Personally, I find that points to the banking system and how usury is a concealed weapon for funnelling the world's resources into the hands of those who control it.
It has also been suggested that 666 becomes unholy when an unholy person claims to identify themselves with the Sun/Son. It is not the number itself that is the problem, but the fact that an individual claims that number for him or herself.
So many thoughts, so few answers.