Belphegor's prime number Belphegor's prime number is a palindromic prime number with a 666 hiding between 13 zeros and a 1 on either side. The ominous number can be abbreviated as 1 0(13) 666 0(13) 1, where the (13) denotes the number of zeros between the 1 and 666. Although he didn't "discover" the number, scientist and author Cliff Pickover made the sinister-feeling number famous when he named it after Belphegor (or Beelphegor), one of the seven demon princes of hell. The number apparently even has its own devilish symbol, which looks like an upside-down symbol for pi. According to...