Oh, c'mon...
The actual historical significance of the number 666 was its application in very ancient numerology as associated with astrology. Ancient numerical systems were derived from their respective alphabets (e.g., Roman numerals from the Latin alphabet). It was a common enough practice to add up the letters in one's name in order to determine "the number of a name" for the sake of making some kind of statement, however bogus, about the significance of one's life. Numbers like 1, 2, 3, 6, 7 & 12 (to name a few) had rather more significance with respect to "destiny" or "purpose" than many other numbers like, say... 157.
Okey, dokey, so what's the deal with 666? Glad you asked! In the Zodiac there are 12 houses. Each house had 3 rooms to a grand total of 36 rooms. One of the most "powerful" numbers in the astrological numerology was 666, actually. Works like this: 1+2+3+... ...+34+35+36 = 666! Once upon a time... soothsayers used "magic squares" to foretell one's fortune by throwing the dice, bones, stones or whatever (as many methods as there were soothsayers) on the square. The Square of the Sun was a six-by-six square: all the numbers from 1 through 36 arranged on the square such that the sum of any single row was 111. Six rows of 111 is... 666, or the number of the Sun God.
So... are there any titles or names in the Roman language that total up to that number? Hmm... try adding up Vicarivs Filii Dei.
Oh, by the way... you know those UPC product bar codes often found on stuff that you buy like this one (if this link works and continues to do so):
See the two narrow lines that are parallel on the far left, far right and in the middle? Those are the field markers and in each case represent "six". The two fields (one on the left; the other on the right) are essentially negatives of each other--one's black on white while the other is white on black. Make of that what you will.