Belphegor's prime

Belphegor's prime is the palindromic prime number 1000000000000066600000000000001 (10 + 666 × 10 + 1), a number which reads the same both backwards and forwards and is only divisible by itself and one.

In the short scale, this number would be named "one nonillion, sixty-six quadrillion, six hundred trillion one." In the long scale, this number's name would be "one quintillion, sixty-six billiard, six hundred billion one."