# 666 (number)

666 (six hundred [and] sixty-six) is the natural number following 665 and preceding 667.

 ← 665 666 667 →
Cardinalsix hundred sixty-six
Ordinal666th
(six hundred sixty-sixth)
Factorization2 × 32 × 37
Greek numeralΧΞϚ´
Roman numeralDCLXVI
Greek prefixἑξακόσιοι ἑξήκοντα ἕξ
hexakósioi hexēkonta héx
Latin prefixsescenti sexaginta sex
Binary10100110102
Ternary2202003
Senary30306
Octal12328
Duodecimal47612
Chinese numeral六百六十六
Devanagari numeral६६६

In Christianity, 666 is called the "number of the beast" in (most manuscripts of) chapter 13 of the Book of Revelation of the New Testament.

## In mathematics

666 is the sum of the first 36 natural numbers ($\sum _{i=1}^{36}i$ , i.e. 1 + 2 + 3 + ... + 34 + 35 + 36 = 666), and thus it is a triangular number. Because 36 is also triangular, 666 is a doubly triangular number. Also, 36 = 15 + 21; 15 and 21 are also triangular numbers, and 152 + 212 = 225 + 441 = 666.

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 prime factorization of 666 is 2 ⋅ 32 ⋅ 37. Also, 666 is the sum of the squares of the first seven primes: $2^{2}+3^{2}+5^{2}+7^{2}+11^{2}+13^{2}+17^{2}$

The number of integers which are relatively prime to 666 is 6 ⋅ 6 ⋅ 6 and the number of twin primes less than $6^{6}$  + 666 is 666.

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).

## In religion

### Number of the beast

In the Textus Receptus manuscripts of the New Testament, the Book of Revelation (13:17–18) cryptically asserts 666 to be "the man's number" or "the number of a man" (depending on how the text is translated) associated with the Beast, an antagonistic creature that appears briefly about two-thirds into the apocalyptic vision. Some manuscripts[which?] of the original Koine Greek use the symbols χξϛ chi xi stigma (or χξϝ with a digamma), while other manuscripts spell out the number in words.

In modern popular culture, 666 has become one of the most widely recognized symbols for the Antichrist or, alternatively, the devil. Earnest references to the number occur both among apocalypticist Christian groups and in explicitly anti-Christian subcultures. References in contemporary Western art or literature are, more likely than not, intentional references to the Beast symbolism. Such popular references are therefore too numerous to list.

It is common to see the symbolic role of the integer 666 transferred to the numerical 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.

The Number of the Beast is cited as 616 in some early biblical manuscripts, the earliest known instance being in Papyrus 115.

## Humour

Mathematicians and others have created a meme with the square root of 666, that is 25.8069. The saying goes, "If 666 is evil, then is 25.8069 the root of all evil?"