The biblical number of the beast, 666, is covered in this chapter. US Route 666, known as the Highway of the Beast, was renamed Route 491 in 2003 after controversy in connection with the beast number. Intel introduced the 666 MHz Pentium III CPU in 1999, but it was marketed as the Pentium III 667 instead of the Pentium III 666. Mathematically, 666 contains delightful curiosities like ‘the sum of cubes of ascending and descending numbers is 666, i.e., 13 + 23 + 33 + 43 + 53 + 63 + 53 + 43 + 33 + 23 + 13 = 666’. In this chapter, you will also see why people tend to believe in such superstition, what the effect is, and what is so fascinating about the number 666. Interesting magic squares connected with the number 666, along with some interesting observations, are also covered in this chapter.