2006-08-16 12:53:01 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Astronomy & Space
28 is the second perfect number
a number is called perfect when all of its factors (except itself) add up to that number. 1+2+4+7+14=28
many more properties associated with perfects can be found at my source, such as how all are derived from certain triangular numbers, but the information is presented in a highly technical format
2006-08-16 13:39:41 · answer #1 · answered by gylbertpenguin 2 · 0⤊ 0⤋
23 is prime. 28 is a perfect number; the sum of its divisors=28. 1+2+4+7+14=28.
2006-08-16 21:28:17 · answer #2 · answered by zee_prime 6 · 0⤊ 0⤋
23 can be changed to 28 with a pencil. 28 can be changed to 23 with an eraser.
2006-08-16 21:23:39 · answer #3 · answered by Kes 7 · 0⤊ 0⤋
Not really. 23 itself is prime. 28 is not.
2006-08-16 19:58:05 · answer #4 · answered by a_liberal_economist 3 · 0⤊ 0⤋