666 (number) on 1/149 in base 10 has a magic total of 666. The prime factorization of 666 is 2 • 3 • 37. Also, 666 is the sum of squares of first seven primes: formula_2 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 the Textus Receptus manuscripts of the New Testament, the Book of Revelation () cryptically asserts 666 to be "man's number" or "the number of a
Latin numerals (linguistics) singular meaning, for example 'a letter', 'a camp', 'a set of chains', '(a set of) clothes', 'winter quarters', 'wedding', 'quadriga' etc. A special series of numeral adjectives was used for counting these, namely , , , , , , and so on. Thus Roman authors would write: "ūnae litterae" 'one letter', "trīnae litterae" 'three letters', "quīna castra" 'five camps', etc. Except for the numbers 1, 3, and 4 and their compounds, the plurale tantum numerals are identical with the distributive numerals (see below). Another set of numeral adjectives, similar to the above but differing in the adjectives for 1, 3,