Hexakosioihexekontahexaphobia

Happy Now Cartoon #666 is up! Some kind of anniversary...

From my friends at Wikipedia:

666 is the natural number following 665 and preceding 667. It is also an abundant number. It 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 formn(n + 1)(n² + n + 2) / 8 (doubly triangular numbers, A002817).

The number of prime numbers up to 666 is 121, the square of the number of prime numbers up to 36.

666 is the 60th 12-factored number; 60 is the first 12-factored number.

666=(3⁶) − (2⁶) + 1; 6=(3²) − (2²) + 1; 66=(3⁴) − (2⁴) + 1.

666 is the sum of the squares of the first seven prime numbers (i.e.2² + 3² + 5² + 7² + 11² + 13² + 17² = 666).

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 palindromic number, a repdigit 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 representation of the number 666 (DCLXVI) uses once each the Roman numeral symbols with values under 1,000, occurring in descending order of their respective values (D = 500, C = 100, L = 50, X = 10, V = 5, I = 1).

666 is a member of the Indices of prime Padovan sequence, 3, 4, 5, 7, 8, 14, 19, 30, 37, 84, 128, 469, 666, 1262, 1573, 2003, 2210, ... (sequence A112882 in OEIS).

And...

It is not uncommon to see the symbolic role of the integer 666 transferred to the digit sequence 6-6-6. Some people take the satanic associations of 666 so seriously that they actively avoid things related to 666 or the digits 6-6-6. This is known as hexakosioihexekontahexaphobia.