Divisor Sum of 2

Example of Divisor Sum of Prime Number

$\map {\sigma_1} 2 = 3$

where $\sigma_1$ denotes the divisor sum.

Proof

From Divisor Sum of Prime Number:

$\map {\sigma_1} p = p + 1$

where $p$ is a prime number.

We have that $2$ is a prime number.

Hence:

$\map {\sigma_1} 2 = 2 + 1 = 3$

$\blacksquare$