Can I used the octopus card on HK Airport Bus?

Hi..It is our first time visiting Hongkong and I'm not familiar on the place were we staying. Our plan is to take Bus A21 from the airport and take off at bus stop #9 since we're booked at Casa Hotel. This plan is based on the map that I saw online. It said that it takes 45-60 minutes to get there, but i guess this is the easiest way.