A repunit is a number using only one digit The numbers 11 and 1111111111111111111 are examples of repunit primes The number of ones in such a repunit primes can be 2 19 23 317 1031 49081 86453 or 109297 An almost repunit number repeats a digit but one digit is different for example 222222922 The primes of this form make interesting patterns as shown in this Demonstration Whether there is any pattern to these is an unsolved problem