The tau function $𝜏 (n)$ was defined in Chapter 1 as the number of positive factors of n. For example,
$𝜏 (12) = 6$ because 12 has factors 1, 2, 3, 4, 6, 12.
Show that for a prime number, $p$, we have $𝜏 (p) = 2$.
A prime $p$ has only 2 positive factors, 1 and $p$, and so the number is 2.
$$ \tau(p) = 2 $$