Beast Number 666
Numerology
"Here is wisdom. Let him that hath understanding count the number of the beast: for it is the number of man; and his number is Six hundred three score and six."
Revelation 13:18 Holy Bible
The "beast number" has several interesting properties that attract numerologists. It is equal to the squares of the first 7 primes
22 + 32 + 52 + 72 + 112 + 132 + 172 = 666
and is a sum and difference of the first three 6th powers.
16 - 26 + 36 = 666
In addition, there are two ways to insert a plus sign "+" into the sequence 123456789 to make the 666, and exactly one way if the digits are reversed to be 987654321.
1 + 2 + 3 + 4 + 567 + 89 = 666
123 + 456 + 78 + 9 = 666
9 + 87 + 6 + 543 + 21 = 666
It is also a triangular number: T36 = 666.
A number having 666 digits has the ominous name of an "Apocalyptic Number."