Facebook has 945 million mobile monthly active users

"Revenue for the full year 2013 was $7.87 billion, an increase of 55% year-over-year.
Income from operations for the full year 2013 was $2.80 billion.
Net income for the full year 2013 was $1.50 billion.
Free cash flow for the full year of 2013 was $2.85 billion.
Daily active users (DAUs) were 757 million on average for December 2013, an increase of 22% year-over-year.
Mobile DAUs were 556 million on average for December 2013, an increase of 49% year-over-year.
Monthly active users (MAUs) were 1.23 billion as of December 31, 2013, an increase of 16% year-over-year.
Mobile MAUs were 945 million as of December 31, 2013, an increase of 39% year-over-year."
Source:  Q4 2013 Earnings release from Facebook, 29th January 2013
Full details of earnings here