The Number 666: Properties and MeaningsPrime Factors of 666=2x3x3x37.
666 is a Triangular Number.
666 is a 223-gonal Number.
342= 666 in base 7.
666 lists in their proper order the letters used for numbers in Roman numeration system, namely D (500) + C (100) + L (50) + X (10) + V (5) + I (1), or DCLXVI.
666 is the sum of the squares of two consecutive Triangular Numbers: (15x15) + (21x21).
666 is the sum of two consecutive palindromic primes 313 + 353.
In the King James Version of the Bible, 'Revelation 13:18': "Here is wisdom: let him who hath understanding count the number of the beast: for it is the number of a man; and his number is 'six hundred three score and six'.
The Year 666 ADThe year 666 AD was at one time considered the date for the advent of the Antichrist.