In recreational mathematics, a repunit's a number like 11, 111, or 1111 that contains only the digit 1. The term stands for repeated unit and was coined in 1966 by Albert H. Beiler. A repunit prime's a repunit that's also a prime number. Definition The repunits base b are defined mathematically as » R_n^nge1. In fact, the base-2 repunits are the well-respected Mersenne numbers Mn = 2n − 1. The Cunningham project endeavours to document the integer factorizations of (among other numbers) the… (More on Repunit)