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.

perfect number

noun

1. an integer, such as 28, that is equal to the sum of all its possible factors, excluding itself

perfect number

1. 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.

Word History and Origins

Origin of perfect number¹

Middle English word dating back to 1350–1400

Example Sentences

It’s natural to pursue the ideal testosterone levels or the perfect number of reps per set—we want to be our best.

From Popular-Science

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

From Project Gutenberg

A perfect number (Greek), as already stated, is one which is equal to the sum of its divisors.

From Project Gutenberg

Seven was, among the Hebrews, their perfect number; and hence we see it continually recurring in all their sacred rites.

From Project Gutenberg

I have gathered thousands of them in my rambles, and the same perfect number is found in every one.

From Project Gutenberg

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.

From Project Gutenberg