A composite number can be factored many different ways. For instance, not including multiplication by one, $24$ can be factored in $7$ distinct ways:

$$\begin{array}{rl}24& =2\times 2\times 2\times 3\\ 24& =2\times 3\times 4\\ 24& =2\times 2\times 6\\ 24& =4\times 6\\ 24& =3\times 8\\ 24& =2\times 12\\ 24& =24\end{array}$$

Recall that the digital root of a number, in base $10$, is found by adding together the digits of that number, and repeating that process until a number is arrived at that is less than $10$. Thus the digital root of $467$ is $8$.

We shall call a Digital Root Sum (DRS) the sum of the digital roots of the individual factors of our number.
The chart below demonstrates all of the DRS values for $24$.

Factorisation	Digital Root Sum
$2\times 2\times 2\times 3$	$9$
$2\times 3\times 4$	$9$
$2\times 2\times 6$	$10$
$4\times 6$	$10$
$3\times 8$	$11$
$2\times 12$	$5$
$24$	$6$

The maximum Digital Root Sum of $24$ is $11$.
The function $\mathrm{mdrs}(n)$ gives the maximum Digital Root Sum of $n$. So $\mathrm{mdrs}(24)=11$.
Find $\sum \mathrm{mdrs}(n)$ for $1<n<1000000$.