perfect number
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enMaths in a minute: Perfect numbers
https://plus.maths.org/content/maths-minute-perfect-numbers
<p>A perfect number is a natural number whose divisors add up to the number itself. The number 6 is a perfect example: the divisors of 6 are 1, 2 and 3 (we exclude 6 itself, that is, we only consider proper divisors) and</p><p>
1+2+3 = 6.</p><p>
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<img src="https://plus.maths.org/content/sites/plus.maths.org/files/blog/072014/monster.jpg" width="250" height="234" alt="Monster"/>
<p>If a non-perfect number were an animal, it might look something like this.</p><p><a href="https://plus.maths.org/content/maths-minute-perfect-numbers" target="_blank">read more</a></p>https://plus.maths.org/content/maths-minute-perfect-numbers#commentsperfect numberWed, 30 Jul 2014 15:28:07 +0000mf3446148 at https://plus.maths.org/contentMaths in a minute: Number mysteries
https://plus.maths.org/content/maths-minute-number-mysteries
<p>Number theory is famous for problems that everyone can understand and that are easy to express, but that are fiendishly difficult to prove. Here are some of our favourites.</p>
<h3>The Goldbach conjecture</h3>
<p>The Goldbach conjecture is named after the mathematician <a href="http://www-history.mcs.st-and.ac.uk/Biographies/Goldbach.html">Christian Goldbach</a> who formulated it in the middle of the eighteenth century. It states that any even natural number greater than 2 can be written as the sum of two prime numbers. </p><p><a href="https://plus.maths.org/content/maths-minute-number-mysteries" target="_blank">read more</a></p>https://plus.maths.org/content/maths-minute-number-mysteries#commentsGoldbach ConjectureMersenne primeMersenne searchnumber theoryperfect numberTue, 16 Jul 2013 08:49:15 +0000mf3445925 at https://plus.maths.org/content