Twitter has 271m monthly active users, and 211m mobile monthly active users

"Average Monthly Active Users (MAUs) were 271 million as of June 30, 2014, an increase of 24% year-over-year.
Mobile MAUs reached 211 million in the second quarter of 2014, an increase of 29% year-over-year, representing 78% of total MAUs.
Timeline views reached 173 billion for the second quarter of 2014, an increase of 15% year-over-year.
Advertising revenue per thousand timeline views reached $1.60 in the second quarter of 2014, an increase of 100% year-over-year.
Advertising revenue totaled $277 million, an increase of 129% year-over-year.
Mobile advertising revenue was 81% of total advertising revenue.
Data licensing and other revenue totaled $35 million, an increase of 90% year-over-year.
International revenue totaled $102 million, an increase of 168% year-over-year.
International revenue was 33% of total revenue.
Net loss – GAAP net loss was $145 million for the second quarter of 2014 compared to a net loss of $42 million in the same period last year. Twitter's GAAP net loss included $158 million of stock-based compensation expense."
Source:  Twitter's Q2 2014 Results, 29th July 2014