Divisor Sum of 3

Example of Sigma of Prime Number

 * $\sigma \left({3}\right) = 4$

where $\sigma$ denotes the $\sigma$ function.

Proof
From Sigma of Prime Number:
 * $\sigma \left({p}\right) = p + 1$

where $p$ is a prime number.

We have that $3$ is a prime number.

Hence:
 * $\sigma \left({3}\right) = 3 + 1 = 4$

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