666/Historical Note

Historical Note on $666$ (Six Hundred and Sixty-Six)
$666$ is the famous Number of the Beast of the Book of the Revelation:
 * Here is wisdom. Let him that hath understanding count the number of the beast: for it is the number of a man; and his number is Six hundred threescore and six.
 * -- The Book of Revelation, chapter 13, verse 18

Hence its reputation as a number traditionally associated with the occult.

Less well known is the fact that the number also appears in the Book of Kings:
 * Now the weight of gold that came to Solomon in one year was six hundred threescore and six talents of gold.
 * -- The First Book of Kings, chapter 10, verse 14

It is also the number that can be formed by all the Roman numerals less than $\mathrm M$ used once each:
 * $666 = \mathrm {DCLXVI}$

It is possible that $666$ was merely chosen as a representative example of some large unspecified number, in the same way that $101$ or $1001$ is frequently so used in contemporary milieux.

However, its other properties make it far more interesting than that.