Shirali, Shailesh
(2018)
On divisibility by 27.
At Right Angles, 7 (1).
pp. 62-65.
Abstract
Notation. We denote the sum of the digits of a positive integer n
by SD(n). The notation a | b means: ‘a is a divisor of b’, i.e., ‘b is
a multiple of a.’ Throughout, we work in base 10.
Two well-known statements. The following two statements are
very well-known:
(1)A positive integer n is divisible by 3 if and only if SD(n) is
divisible by 3.
(2)A positive integer n is divisible by 9 if and only if SD(n) is
divisible by 9.
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