Justin Timberlake is a genius: Rihanna

London: R&B singer Rihanna is all praises about pop star Justin Timberlake, calling him a "genius" in songwriting.

The `Umbrella` hitmaker teamed up with the 28-year-old singer on the hit single `Rehab` and Rihanna admits she has learned a lot from him in the studio, Contactmusic reported.

"Working with Justin in the studio is just great. He`s a fun guy and likes to make all the sessions enjoyable. He`s also such a genius when it comes to lyrics," said the Grammy-award-winning singer.

Rihanna also has great regards for her mentor rapper Jay-Z, who signed her to Def Jam Recordings when he was label president, and from whom she has learned a lot about music and life in general.

“From Jay-Z I`ve also learned a lot. He is more of a mentor in general, not just for music but he gives good all-round advice," said the singer.

The 22-year-old, who is dating baseball star Matt Kemp, is currently on the European leg of her `Last Girl on Earth` tour and admitted that she never done a tour of this capacity.

"We`ve never done a tour to this capacity. The production is unbelievable and so are the costumes, we just took it to a whole new level. We just keep growing," said Rihanna.