Only one, the second one is yet to be finished.
two
antonov airlines
The Antonov An-225 by far.
one
Wikipedia: "The first An-225 was completed in 1988 and a second An-225 has been partially completed. The one An-225 is in commercial operation with the Antonov Airlines carrying over-sized payloads."
One may find out information about the Antonov 225 via the 'Airlines' website, from watching YouTube videos posted on the Youtube website or by visiting the Wikipedia page for Antonov 225.
Its Antonov 225...
Antonov 225 Myria
The Antonov An-225
the antonov 225
Antonov 225
Antonov An-225.