Blackjack21 is one of several free casino games you download at Google Play. Players using this game on mobile devices require Android operating systems. Blackjack21 free casino games require Android 4.0.3 and up. The game rates as Teen and has interactive elements to make simulated gaming fun and exciting. The most recent update from the developers is for September 1, 2017. They keep the game current and update frequently. This free casino game is currently in version 6.6.0. Players install this game between 1,000,000 – 5,000,000 times attesting to its popularity.