Divisor Count of 90

Example of Use of $\tau$ Function

 * $\tau \left({90}\right) = 12$

where $\tau$ denotes the $\tau$ Function.

Proof
From Tau Function from Prime Decomposition:
 * $\displaystyle \tau \left({n}\right) = \prod_{j \mathop = 1}^r \left({k_j + 1}\right)$

where:
 * $r$ denotes the number of distinct prime factors in the prime decomposition of $n$
 * $k_j$ denotes the multiplicity of the $j$th prime in the prime decomposition of $n$.

We have that:
 * $90 = 2 \times 3^2 \times 5$

Thus:

The divisors of $90$ can be enumerated as:
 * $1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 90$