From an original 1863 Louis le Breton's illustration

Belphegor is described in Kabbalistic writings as the "disputer", the counterpart of the sixth Sephiroth "beauty". When summoned, he can grant riches, the power of discovery and ingenious invention. His role as a demon was to sow discord among men and seduce them to evil through the apportionment of wealth.

The palindromic prime number 1000000000000066600000000000001 is known as Belphegor's prime, due to the significance of containing the number 666, on both sides enclosed by thirteen zeroes and a one. An entire sequence of "palindromic Belphegor numbers" is formed from computing (10^(n+3)+666)*10^(n+1)+1 for different values of n: 16661, 1066601, 100666001, 10006660001, 1000066600001, 100000666000001, 10000006660000001, 1000000066600000001, 100000000666000000001, 10000000006660000000001, 1000000000066600000000001, 100000000000666000000000001, 10000000000006660000000000001, 1000000000000066600000000000001. All of these numbers are palindromic and contain "666", but only the first and last are prime.