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# perfect number

noun, Mathematics.
1.
a positive number that is equal to the sum of all positive integers that are submultiples of it, as 6, which is equal to the sum of 1, 2, and 3.
Origin of perfect number
1350-1400
Middle English word dating back to 1350-1400
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for perfect number
Historical Examples
• But here again he was uncertain whether the ‘perfect number’ was ten or six.

Various
• Seven was a perfect number, and therefore the victims should be seven.

W. G. Blaikie
• Canaan is a type of holiness, and seven is the perfect number.

W. E. Shepard
• Thousand is a perfect number, and no number extends beyond it.

• Ten was a perfect number, and is that of the commandments given to Moses.

• The perfect number mentioned in the present passage is the number ten.

Dante Alighieri
• And in reply, another remarked, 'Seven is the perfect number, and seven times seven is perfection.'

Harriet Beecher Stowe
• Therefore, too, Aristotle thought there were five elements, since the uneven and perfect number had everywhere the predominance.

Plutarch
• Six was a perfect number—that is, equal to the sum of all its factors—an additional reason why there must be exactly six planets.

• “There are never more than seven crackers on a plate—just seven, the perfect number,” sighed this hyperbolical girl.

Annie Roe Carr
British Dictionary definitions for perfect number

## perfect number

noun
1.
an integer, such as 28, that is equal to the sum of all its possible factors, excluding itself
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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perfect number in Science
 perfect number   A positive integer that equals the sum of all of its divisors other than itself. An example is 28, whose divisors (not counting itself) are 1, 2, 4, 7, and 14, which added together give 28.
The American Heritage® Science Dictionary