Noun
perfect number (plural perfect numbers)
(number theory) A number that is the sum of all of its divisors except itself.
The factors of 6 are 1, 2, 3 and 6, and 1 + 2 + 3 = 6, so 6 is a perfect number.
The factors of 28 are 1, 2, 4, 7, 14 and 28, and 1 + 2 + 4 + 7 + 14 = 28, so 28 is a perfect number.
Personally, I think four is the perfect number of children for our particular family. Four is enough to create the frenzied cacophony that my husband and I find so joyful. Ayelet Waldman
Euclid also proved a formation rule (IX.36) whereby is an even perfect number whenever is what is now called a Mersenne prime —a prime of the form for prime Much later, Euler proved that all even perfect numbers are of this form. Source: Internet
A semiperfect number that is equal to the sum of all its proper divisors is a perfect number. Source: Internet
In a manuscript written between 1456 and 1461, an unknown mathematician recorded the earliest European reference to a fifth perfect number, with 33,550,336 being correctly identified for the first time. Source: Internet
Aristotle suggests that it was also introduced "to raise the number of heavenly bodies around the central fire from nine to ten, which the Pythagoreans regarded as the perfect number". Source: Internet
In 1496, Jacques Lefèvre stated that Euclid's rule gives all perfect numbers, citation thus implying that no odd perfect number exists. Source: Internet