84.09 Digital roots and reciprocals of primes

Abstract

The digital root of a number is found by adding its digits, then adding the digits of the result, and so on, until a single digit is obtained. For example: 142857-»27->9. Most readers will be aware that the digital root is equivalent to the starting number modulo 9. Recently I computed the digital roots of the recurring parts of the decimal representations of prime reciprocals (Table 1). Prime Reciprocal as a decimal Digital