Set a timer for 21 minutes to wake you up in 21 minutes. This is a free and easy-to-use countdown timer that allows you to set the hour, minute, and second for the online countdown. Simply start the timer, and it will alert you when 21 minutes have passed. Alternatively, you can set a specific date and time to count down to (or from) an event. Begin your 21 minutes timer now for a quick and precise reminder.