Is 21 a deficient number and what is its deficiency?

Is 21 a deficient number?

Here we will explain and calculate if 21 is a deficient number and its deficiency if applicable.

21 is a deficient number if the sum of its proper divisors is less than 21.

The sum of its proper divisors is calculated as follows: 1 + 3 + 7 = 11.

11 is less than 21. Therefore, 21 is a deficient number.

The deficiency of 21 is 21 minus the sum of its proper divisors. Thus, the deficiency of 21 is 21 - 11 = 10

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