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
Abjad numerals alternative Abjad order. For four Persian letters these values are used: The Abjad numerals are equivalent to the earlier Hebrew numerals up to 400. The Hebrew numeral system is known as Gematria and is used in Kabbalistic texts and numerology. Like the Abjad order, it is used in modern times for numbering outlines and points of information, including the first six days of the week. The Greek numerals differ in a number of ways from the Abjad ones (for instance in the Greek alphabet there is no equivalent for , ""). The Greek language system of letters-as-numbers is called isopsephy.