Sirius XM Radio says it ended the year with nearly 21.9 million subscribers. It reported approximately 540,000 net new subscribers in the fourth quarter and approximately 1.7 million paying customers for the full year 2011.

The satcaster had previously projected full year subscriptions would increase to 21.6 million.

Company CEO Mel Karmazin said based on preliminary subscriber data that SiriusXM exceeded its subscriber guidance for the year. “Our subscriber growth accelerated in 2011 as net additions grew approximately 20%, delivering our best year for net additions since the merger and demonstrating the strong continuing demand for our unmatched audio content.”

The company expects complete 2011 results in February.