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How is 20 a perfect number?
It isn't a perfect number.A perfect number is a number which is the sum of its proper divisors (including 1, but excluding itself).The divisors of 20 are 1, 2, 4, 5, 10.1 + 2 + 4 + 5 + 10 = 22 => 20 is not a perfect number.An example of a perfect number is 28:The divisors of 28 are 1, 2, 4, 7, 141 + 2 + 4 + 7 + 14 = 28 => 28 is a perfect number.
Is 8128 a abundant deficient or perfect number?
abundant since sum of divisors is 16256
Why 21 is not a perfect number?
First, you want to know the definition of a perfect number: A perfect number is an integer which is equal to the sum of all its positive integer divisors that are less than itself. Example: The positive integer divisors of 6, less than 6, are 1, 2, and 3. The sum of those divisors is 1 + 2 + 3 = 6. Therefore, 6 is a perfect number. Now, 21 does not meet this definition and therefore is not a perfect number. Let's try it. There are three positive divisors of 21, namely, 1, 3, and 7, that are less than 21, itself. (There are no others.) But the sum of these divisors is 1 + 3 + 7 = 11, which is not equal to 21. Therefore, we confirm that 21 is not a perfect number.
How can you tell if a number is abundant perfect or deficient?
Find the sum of the proper divisors of that number.a perfect number equals the sum of its proper divisorsa deficient number is greater than the sum of its proper divisorsan abundant number is less than the sum of its proper divisors
Why are no prime numbers perfect numbers?
Prime numbers have two factors. The sum of their proper divisors is always 1.
