Question

Which of the following numbers are perfect numbers?

• A. whose sum of all its factors is equal to twice the number.
• B. 27
• C. whose sum of all its factors is equal to thrice the number.
• D. none of these

Answer 1

Answer: (B), (C)

The correct options are
B

27

C

whose sum of all its factors is equal to thrice the number.

Sum of all the factors of a perfect number will be equal to double of the number.

6 is a perfect number since the sum of its factors 1, 2, 3 and 6 is 12 i.e. twice of 6.
28 is a perfect number because the sum of its factors 1, 2, 4, 7, 14, 28 is 56.