Question

Which of the following is perfect number ?

• A. $6$
• B. $7$
• C. $8$
• D. $9$

Answer 1

Answer: (A)

$6$

A number is called a perfect number if by adding all the positive divisors of the number (except itself), the result is the number itself.

$\left(a\right)6$ is the first perfect number. Its divisors (other than the number itself: $6$) are $1,2,$ and $3$ and $1+2+3=6$.

$\left(b\right)7$ is the not a perfect number. Its divisors (other than the number itself: $7$) are $1$ and $1\ne 7$.

$\left(c\right)8$ is the not a perfect number. Its divisors (other than the number itself: $8$) are $1,2$ and $4$ and $1+2+4=7\ne 8$.

$\left(d\right)9$ is the not a perfect number. Its divisors (other than the number itself: $9$) are $1$ and $3$ and $1+3=4\ne 9$.