UPDATE 1-SiriusXM to buy Pandora in $3.5 bln stock deal

(Adds details on details, advisers, shares)

Sept 24 (Reuters) - Satellite radio company Sirius XM Holdings Inc said on Monday it would buy music-streaming service provider Pandora Media Inc in an all-stock deal valued at about $3.5 billion.

Pandora shareholders will receive a fixed-exchange ratio of 1.44 newly-issued SiriusXM shares for each share they hold.

The implied price of Pandora common stock is $10.14 per share, the companies said, representing a premium of 11.55 percent to stock's Friday close.

Pandora's shares rose 18.4 percent to $10.75 in premarket trading.

SiriusXM currently owns convertible preferred stock in Pandora that represents a stake of about 15 percent on an as-converted basis, the companies said.

The transaction is expected to close in the first quarter of 2019.

Pandora has faced brutal competition from bigger rivals Spotify, Apple Music and Google's Play Music, and has been launching new features to woo more subscribers as part of a turnaround aimed at achieving profitability.

Allen & Co LLC and BofA Merrill Lynch are financial advisers to SiriusXM and Baker Botts LLP and Simpson Thacher & Bartlett LLP are providing legal counsel.

Centerview Partners LLC, LionTree Advisors LLC and Morgan Stanley & Co LLC are financial advisers to Pandora and Sidley Austin LLP is the legal counsel. (Reporting by Vibhuti Sharma in Bengaluru; Editing by Sriraj Kalluvila)