Nov 21, 2009
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What Is A Perfect Number?

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Read Latest Entries..: (Post #27) by miladinoski on Jan 18 2009, 10:20 PM.
Wow. I knew that something like 'perfect' number existed but I thought that it was only one though I didn't know which one is it. I guessed that it was 42 like one of the repliers said I saw the Wikipedia page and it explains it perfectly how you can get a perfect number with one formula QUOTE for n = 2: 21(22 − 1) = 6for n = 3: 212(23 − 1) = 28for n = 5: 24(25 − 1) = 496for n = 7: 26(27 − 1) = 8128I wonder what would have been if the Greeks had a simp...
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Open Discussion > xisT-O-Rama > Life Talk > Science and Nature

What Is A Perfect Number?

beeseven
A perfect number is a number with the property that all of its divisors (including 1 but excluding itself) add up to that number. Alternatively, if you want to include the number as a divisor, then all of its divisors add up to twice itself.

Some examples include:
  • 6 (1+2+3)
  • 28 (1+2+4+7+14)
  • 496 (1+2+4+8+16+31+62+124+248)
  • 8128 (1+2+4+8+16+32+64+127+254+508+1016+2032+4064)

It used to be thought that the fifth perfect number would have five digits since the others had 1, 2, 3, 4, but it turns out that the fifth is 33550336 which has eight digits. It was also thought that the endings would alternate between 8 and 6, but the sixth perfect number is 8589869056. There most likely aren't any odd perfect numbers, but if there are, they are extremely large (> 10^500).

Wikipedia has more, including the conditions which an odd perfect number must satisfy and the proof that all perfect numbers are also Ore's harmonic numbers.

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unicornrose
Its not too surprising to me that when you got to the 6th number the amount of digets got larger. Math has alot of differant sequences that tend to do that. Just like nature sometimes math can throw you for a loop. smile.gif

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Dooga
Hey this is really interesting! I would show it to my math teacher, but then she'll shoot me for wasting my time...

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hulunes
the perfect number remind me a former program in C,which is to carry out the procedure of quering the number of that kind during 10000.
well.it is really a interesting math number IMO. smile.gif

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Plenoptic
It's funny you made this post because in computer programming I was just told to make a program that will display the pefect numbers found between 1 and 1000. I think it is pretty interesting how it works. Of course it took me a while to get the equation right to have it find the numbers.

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Florisjuh
Sounds very interesting, but what's the use of it?

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Alissa
That's really cool. Can you imagine being the person who first found these perfect numbers? It's insane. I could never. O.O

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leeleelee
It is not known when perfect numbers were first studied and indeed the first studies may go back to the earliest times when numbers first aroused curiosity. It is quite likely, although not certain, that the Egyptians would have come across such numbers naturally given the way their methods of calculation worked, see for example where detailed justification for this idea is given. Perfect numbers were studied by Pythagoras and his followers, more for their mystical properties than for their number theoretic properties.

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Plenoptic
Like lee said I think people have known about them they just weren't called Perfect Numbers. I am sure they figured it out soon enough. I wonder how many they have found so far and how many more they will find. I think it will turn out to be like the Largest Prime Number and people will start competing to see who can find one a million characters long unless they have already.

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Justin S.
What are you taling about perfect number?

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Latest Entries

miladinoski
Wow. I knew that something like 'perfect' number existed but I thought that it was only one though I didn't know which one is it. I guessed that it was 42 like one of the repliers said smile.gif

I saw the Wikipedia page and it explains it perfectly how you can get a perfect number with one formula smile.gif
QUOTE
for n = 2: 21(22 − 1) = 6
for n = 3: 212(23 − 1) = 28
for n = 5: 24(25 − 1) = 496
for n = 7: 26(27 − 1) = 8128

I wonder what would have been if the Greeks had a simple calculator laugh.gif

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garbage
I think this topic, is not for me since im not that good at the mathematics, but I was thinking the pefect number might have been zero.. I dont know why, but thats the number tyhat first popped into my head

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BhajunSingh
I find this kind of pure mathematics very interesting personally - its also really amazing to me how people were able to come up with this stuff thousands of years ago.

Also, in case anyone's interested further in perfect numbers, each number has a direct relation with a unique Mersenne Prime number. A Mersenne prime is a prime number in the form of (2^n - 1), where n is also a prime number. So, for example, the first Mersenne prime is 3, where n = 2, the second is 7, where n = 3, and so on. To find the directly related perfect number, you take the Mersenne prime (2^n - 1) and multiply it with (2^(n - 1)).

So for example, with n = 2, the Mersenne prime is 6, and the perfect number is also 6:
CODE

(2^n - 1)(2^(n - 1))
(2^2 - 1)(2^(2 - 1))
(4 - 1)(2^1)
(3)(2)
6


And when n = 3, the Mersenne prime is 7, and the perfect number is 28:
CODE

(2^n - 1)(2^(n - 1))
(2^3 - 1)(2^(3 - 1))
(8 - 1)(2^2)
(7)(4)
28


Hope that makes some sense smile.gif Anyway, so basically, since Mersenne primes are smaller and have more searching formulas, they're used to find more and more perfect numbers...and as there are only 43 known Mersenne primes, there are 43 known perfect numbers. Also, on an off note, Mersenne primes are also the largest primes known...the 43rd MPrime was about 2^30,400,000ish...just over 9 million digits long biggrin.gif

Anyway, I ramble - I just find Mersenne primes especially, and the searching algorithms, very interesting. If anyone else wants to know more about then, http://www.mersenne.org is a good site - it runs the GIMPS (Great Internet Mersenne Primes Search) program that uses distributed computing to attempt to discover new Mersenne primes. wink.gif

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thewildmen2
wow, so interesting, i want to show this to my brother..

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tdktank59
well if we are doing that...

i say the best number is still 42 but my ideal number would be a number that is NOT devisible by 1 lol

figure that one out will ya?

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