666 (number) - Wikipedia
https://en.wikipedia.org/wiki/666_(number)
WEB666 is a Smith number and Harshad number in base ten. The 27th indexed unique prime in decimal features a "666" in the middle of its sequence of digits. The Roman numeral for 666, DCLXVI, has exactly one occurrence of all symbols whose value is less than 1000 in decreasing order (D = 500, C = 100, L = 50, X = 10, V = 5, I = 1).
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