The sum of the natural numbers which are divisors of 100, is :

The correct answer is Option (2) → 217

The divisors of 100 can be listed and added: 1, 2, 4, 5, 10, 20, 25, 50, 100, whose sum is 217.

Shortcut:

• Write the number as a product of prime powers: \(100=2^{2}\times5^{2}\)

• Every divisor is \(2^{a}\times5^{b}\), so the sum of the divisors is the product of the sums of the powers: \((1+2+4)(1+5+25)\)

• \(7\times31=217\)