Answer
20 is not a perfect number.
Work Step by Step
The factors of 20 are: $1, 2, 4, 5, \text{ and } 10$
The sum of the factors is:
$=1+2+4+5+10
\\=22$
The sum of the factors is not equal to 20. Therefore, 20 is not a perfect number.
Thinking Mathematically (6th Edition)
by Blitzer, Robert F.
Published by
Pearson
ISBN 10:
0321867327
ISBN 13:
978-0-32186-732-2
Chapter 5 - Number Theory and the Real Number System - 5.1 Number Theory: Prime and Composite Numbers - Exercise Set 5.1 - Page 256: 77
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