0
You visited us 0 times! Enjoying our articles? Unlock Full Access!
Question

A number n is said to be 'perfect' if the sum of all its divisors (excluding n itself) is equal to n. An example of a perfect number is
  1. 9
  2. 15
  3. 21
  4. 6

A
6
B
9
C
15
D
21
Solution
Verified by Toppr

Lets check each option one by one
A. 9 divisor are 1 and 3.
1+3=49 so not a perfect number.
B. 15 divisors are 1,3, and 5.
1+3+5=915 so not a perfect number
C. 21 divisors are 1, 3 and 7.
1+3+7=1121, so not a perfect number.
D. 6 divisors are 1,2 and 3.
1+2+3=6 It is a perfect number
So correct answer is option D

Was this answer helpful?
3
Similar Questions
Q1
A number n is said to be 'perfect' if the sum of all its divisors (excluding n itself) is equal to n. An example of a perfect number is
View Solution
Q2

In the answer of Question Number 139 it is written -

By definition, a number, for which the sum of all its factors excluding the number itself is equal to twice the number, is called perfect number.

Should it be as below -

a number, for which the sum of all its factors excluding the number itself is equal to the number, is called perfect number.

View Solution
Q3
Let f be a non-negative continuous function defined on R such that f(x)+f(x+12)=6 and N=60f(x) dx. Then
View Solution
Q4
The number of divisors of apbqcrds where a, b, c, d are primes & p, q, r, s ϵ N, excluding 1 and the number itself, is:
View Solution
Q5
The natural number has prime factorization given by N=235x7y, where x+y=5 and 1x+1y=56 (x>y). Then the number of even divisors of N (excluding N), is equal to
View Solution