A repunit is a number whose expansion (in base 10) is a string of ones (for example: 11 and 11111111). A generalized repunit (base b) is one whose expansion base b is all ones. For example, the Mersenne primes are the generalized repunits in base 2. Here is a formula for the n "digit" generalized repunit (base b): (bn-1)/(b-1).
16661 The smallest Beastly prime number
16661 is the 1928th prime, The next Beastly prime to occur, 1000000000000066600000000000001