it also looks like an upsidedown 999It's an interesting number:
666 is the sum of the squares of the first 7 prime numbers: 4+9+25+49+121+169+289=666.
It's also the sum of the first 36 natural numbers (i.e. 1 + 2 + 3 + ... + 34 + 35 + 36 = 666)
just saying