$21USD = $31.23 NZD currently
To find this any day, use Google or any internet search for automatic conversion, just type your search as:
Convert USD to NZD (or New Zealand dollar) this will give you the coversion rate for 1 USD. Then just put 21 into the box with one dollar in the 1 dollar box and it will give you the answer in NZD.
Hope you are a happy Kiwi!