How can I convert an integer like "170526" into its equivalent date (in this case 05/26/17)?

In my spreadsheet, I've got a bunch of dates formatted weird like:

170526
180921
181002
181002
181021

I'd like to use a formula and convert those over to:

05/26/17
09/21/18
etc.

where the first two digits are the year, middle two is the month, and the last two are the day.