Perfect Number

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perfect number

[′pər·fikt ′nəm·bər]
(mathematics)
An integer which equals the sum of all its factors other than itself.

Perfect Number

a positive integer that is equal to the sum of all its factors except itself. Examples of perfect numbers are 6 = 1 + 2 + 3 and 28 = 1 + 2 + 4 + 7 + 14.

As early as the third century B.C., Euclid showed that even perfect numbers could be obtained from the formula 2p–l(2p – 1) when p and 2p – 1 are prime numbers. Approximately 20 even perfect numbers have been found in this way. As of 1976, no odd perfect numbers are known, and their existence remains an open question. Perfect numbers were first investigated by the Pythagoreans, who ascribed a special mystical meaning to such numbers and combinations of such numbers.

perfect number

equal in value to the sum of those natural numbers that are less than the given number but that also divide (with zero remainder) the given number. [Math.: EB, VII: 872]
References in periodicals archive ?
Zola added: "We invested a lot in him this year; we thought he was the perfect number nine for us.
And, not to be missed, are the highly coveted Qatari plate numbers '97400' and '1218', the perfect number to display for National Day.
A Square number B Whole number C Rich number D Perfect number 2.
He also wore number 28 on his uniform, the second smallest perfect number, and the number that serves to end Ogawa's novel.
You'd think Yorkshire dwellers would be all over Yorkshire puddings with their roast opting for more than anyone else, but like the majority of the country they think that two is the perfect number.
Simpson: American Crime Storyf "It's just sitting down and figuring it out" during the outlining process, which led to the decision that "10 is the perfect number; these are the stories we want to tell."
Sanchez left Italy to shine at Barcelona before becoming a hit at the Emirates, and Guidolin said: "Gylfi is very important for me and the team and I hope to have the possibility to work with him in the future because, for me, he is the perfect number 10.
"Wesley Sneijder and Deco are my perfect number 10s.
After a great deal of experimentation, research and application, I stumbled upon the perfect number of New Year's resolutions that actually stand a chance of surviving longer than a brat on a bowl-game grill--one.
Du Wenlong, a fellow at the People's Liberation Army (PLA) Academy of Military Science Research, said earlier the trio of large nuclear-powered aircraft carriers makes for a perfect number because "(http://www.globaltimes.cn/content/894299.shtml) one is always available for operational missions, while the second is used for training and the third is resupplied and retrofitted ."
(54) But twenty-eight has even further numerological significance in addition to being the second perfect number and the number of days in the lunar month as Walker points out.
* While clicking a picture, show eight teeth as it's the perfect number for that beautiful smile.

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