Belphegor’s prime is the palindromic prime number 1000000000000066600000000000001 (1030 + 666 × 1014 + 1), a number which reads the same both backwards and forwards and is only divisible by itself and one. It first discovered by Harvey Dubner, a mathematician known for his discoveries of many large prime numbers and prime number forms. For Belphegor’s prime in particular, he discovered the prime while determining a sequence of primes it belongs to.
The name “Belphegor’s prime” was coined by author Clifford A. Pickover in 2012. Belphegor is one of the Seven Princes of Hell; specifically, ‘the demon of inventiveness.’ The number itself contains superstitious elements that have given it its name: the number 666 at the heart of Belphegor’s prime is widely associated as being the number of the beast, used in symbolism to represent one of the creatures in the apocalypse or, more commonly, the devil. This number is surrounded on either side by thirteen zeroes and is 31 digits in length (thirteen reversed), with thirteen itself long regarded superstitiously as an unlucky number in Western culture.
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