•'666 Wikipedia Bahasa Indonesia' Tehran Chronicle §In mathematics . 666 is the sum of the first 36 natural numbers (i.e. 1 + 2 + 3+ + 34 + 35 + 36 = 666), and thus it is a triangular number. Notice that 36 = 15. 666. Year 666 (DCLXVI) was a common year starting on Thursday (link will display the full calendar) of ...