Rule of Nines

The divisibility test that an integer is divisible by 9 iff the sum of its digits is divisible by 9.

See also

Casting Out Nines, Divisibility Tests

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Flannery, S. and Flannery, D. In Code: A Mathematical Journey. London: Profile Books, pp. 115-116, 2000.

Referenced on Wolfram|Alpha

Rule of Nines

Cite this as:

Weisstein, Eric W. "Rule of Nines." From MathWorld--A Wolfram Web Resource.

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