Answer
$1,600,000$
Work Step by Step
The generalized basic counting principle says that if an event $e_1$ can be performed in $n_1$ ways and an event $e_2$ can be performed in $n_2$ ways, then there are $n_1n_2$ ways of performing them together. This can easily be extended to $n$ events.
Here, we have $8$ choices for the first digit (all digits apart from $0$ and $9$), $2$ choices for the last digit ($2$ or $3$) and $10$ choices (all digits) for the rest of the $5$ middle digits. Thus, using the generalized basic counting principle, the total number of phone numbers is:
$8(10)(10)(10)(10)(10)(2)=1,600,000$
