Chapter 18

Repunits

1 k-right-transposable integers

2 k-left-transposable integers

3 Sam Yates’ repunit riddles

4 Recurring decimals

5 The period length of a prime

Appendix: Factorizations of repunitsRn,n≤ 50

Appendix: Primitive divisors of repunits

Appendix: Multiplicative digital root

Exercise

Project: Period lengths of primes< 100.

Project: A number whose cube root divides all numbers

obtained by cyclic permutations of its digits.