If you think 666 is a spooky number, then you'll be especially creeped out by the "prime number of the beast." But don't worry, numbers don't bite. The prime number of the beast, as it's known, is a giant palindromic number also called Belphegor's Prime. This is the sinisterly named number: 1000000000000066600000000000001. To help you parse that out a bit, that's a 1 followed by 13 zeroes, 666 in the middle, and thirteen more zeroes before another 1 on the end. Scared yet?

Belphegor's Prime was named by American author Clifford A. Pickover. It's a spooky number because 666, which is in the middle of the prime, is known as the number of the beast. On either side of this number are 13 zeroes, and 13 is widely considered an unlucky number. In total, the number has 31 numerals, which is 13 backwards. This prime is named after Belphegor, one of the seven princes of Hell, who is known for tempting people with the gift of discovery and invention. Learn more about this number and anti-primes in the video below.