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Mathematics

Naturally enough, 666 also has many mathematical properties, some more interesting than others:


666 is the 667th natural number.


666 = 2 × 32 × 37 is the 333rd even number and the 544th composite number. (The 666th composite number is 806 = 2 × 13 × 31). 666 is the 260th non square-free number: {4, 8, 9, 12, 16, 18, 20, 24, ..., 648, 650, 652, 656, 657, 660, 664, 666, ...}. The 666th non square-free number is 1701.

666 isn't a prime. The 666th prime is 4973. 666 isn't a lucky number. The 666th lucky number is 5559.


666 has 12 divisors: {1, 2, 3, 6, 9, 18, 37, 74, 111, 222, 333, 666}. The sum of its divisors is 1482. The first numbers in the interval [1, 106] that have the same sum of divisors are 666, 1017, 1481. The sum of its proper divisors is 816>666, so 666 is the 162th abundant number. 666 has 3 distinct prime divisors {2, 3, 37} (&969;(37) = 1+1+1=3) and a total of 4 prime divisors (&937;(666)=...=4).

By Euler's totient function φ(666) = 216. 666 is the 14th number with this value of φ: {247, 259, 327, 333, 351, 399, 405, 436, 494, 518, 532, 648, 654, 666, ...}


The harmonic mean of the digits of 666 is an integer: 3/(1/6 + 1/6 + 1/6) = 6. 666 is the 54th number with this property.

666 is the 25th repdigit.


666 is the 76th palindromic number in base 10 and it is also the sum of two consecutive palindromic primes: 666=313+353. It is the 62th palindromic composite number.

The sum of all the integers from 1 to 36 inclusive is 666. This means 666 is the 36th triangular number. (The 666th triangular number, on the other hand, (1+2+3+...+664+665+666) is 222111.)

but i do. my dear friend