DCLXVI
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Six hundred [and] sixty six is the sum of the first 36 natural numbers (i.e. 1 + 2 + 3 + ... + 34 + 35 + 36 = 666), and thus a triangular number.
Since 36 is both square and triangular, 666 is the sixth number of the form n2(n2 + 1) / 2 (sequence A037270 in OEIS) and the eighth number of the form n(n + 1)(n2 + n + 2) / 8 (doubly triangular numbers) (A002817).
666 is an abundant number.
The number of prime numbers up to 666 is 121, the square of the number of prime numbers up to 36.
666 is the sum of the squares of the first 7 prime numbers: 4+9+25+49+121+169+289=666.
666 is the 60th 12-factored number; 60 is the first 12-factored number.
The harmonic mean of the decimal digits of 666 is (trivially — all repdigit natural numbers have this property) an integer: 3/(1/6 + 1/6 + 1/6) = 6, making 666 the 54th number with this property.
In base 10, 666 is a repdigit (and therefore a palindromic number) and a Smith number. A prime reciprocal magic square based on 1/149 in base 10 has a magic total of 666.
The Roman numeral for 666, DCLXVI, has exactly one occurrence of all symbols whose value is less than 1000 (D=500, C=100, L=50, X=10, V=5, I=1).
666 is a member of the indices of prime Pandovan numbers: 3, 4, 5, 7, 8, 14, 19, 30, 37, 84, 128, 469, 666, 1262, 1573, 2003, 2210, ... (sequence A112882 in OEIS).
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666 is the magic sum, or sum of the magic constants of a six by six magic square, any row or column of which adds up to 111.
The sum of all the numbers on a roulette wheel is 666.[2]
666 was a winning lottery number in the 1980 Pennsylvania Lottery scandal, in which equipment was tampered to favor a 4 or 6 as each of the three individual random digits.[3]
666 was the original name of the Macintosh SevenDust computer virus that was discovered in 1998.
In the Bible, 666 is the number of talents of gold Solomon collected each year (see 1 Kings 10:14, 2 Chronicles 9:13).
In the Bible, 666 is the number of Adonikam's descendants who return to Jerusalem and Judah from the Babylonian exile (see Ezra 2:13).
The number 666 is a frequent visual element of Aryan Brotherhood tattoos.
In Kabbalistic Judaism the number 666 represents the creation and perfection of the world. The world was created in 6 days, and there are 6 cardinal directions (North, South, East, West, Up, Down). 6 is also the numerical value of one of the letters of God's name.[4]
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Some scholars contend that the number 666 is a code for the Roman Emperor Nero.
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The number of the beast is 666 by William Blake.
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Just to point out that the no. 666 is actually DCLXVI in roman numerals, and that D,C,L,X,V and I, in turn, are the first six symbols in the roman numerical system in reverse order (i.e. I, V, X, L, C and D backwards). It's like us writing 9,8,7,6,5,4,3,2,1,0, and then someone coming along to add them all up to get 45!
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