# Depressed Numbers [duplicate]

$12 = 0$
$1234 = 1$
$123456 = 2$
$12345678 = 4$

$369 = 2$
$248 = 3$

$2 = 0$
$3 = 0$
$5 = 0$
$7 = 0$
$11 = 0$
$13 = 0$

What does:
$123456789 = ?$
Why?

Hopefully isn't too hard, please ask if you need any test cases.

• Wow this was way too easy. Really should amp up the difficulty level Jul 16 '15 at 16:05

5

because

You're counting the number of holes in the numbers.

• @JLee Thanks. I didn't know how to do the hide thingy. Jul 16 '15 at 16:08