Okay so ignore my previous post, lol. I made a BIG mistake. xD Forgot to cube things.
The volume is not 1cm cubed = 10,000 micrometres cubed, but 1,000,000,000,000 (so 12 zeros!!!)
So length = 10^12 / (16 x pi)
which gives a length of 19,994,368,226 micrometres
OR 19,994 metres.
That's a lot of metres. xD