Is 1000000000000066600000000000001 a prime

The number 1,000,000,000,000,066,600,000,000,000,001 (10²⁷ + 666 × 10¹⁴ + 1) is indeed a prime number, often referred to as "Belphegor's Prime." This number gained attention among mathematics enthusiasts because of its intriguing palindromic structure: it features the number 666 (sometimes associated with symbolic or cultural significance) surrounded symmetrically by thirteen zeros on each side and bookended by ones. The palindromic property means it reads the same forwards and backwards, though palindromes themselves are not inherently prime or composite.

What makes Belphegor's Prime particularly interesting is that it combines aesthetic appeal with genuine mathematical significance—it's not just a curiosity but a verified prime number. Determining primality for numbers of this magnitude requires computational primality tests like Miller-Rabin or elliptic curve methods, as trial division would be impossibly time-consuming. The number contains 31 digits total, and its prime status has been confirmed through rigorous testing. While this prime has no practical applications in cryptography or computing (which typically use primes of different structures), it serves as an excellent example of how mathematical properties can emerge in unexpected patterns, and it demonstrates that primes can be found in numbers with deliberate, human-interesting structures.