Britney Spears Seen Out for First Time Since Selling Music Catalog

Britney Spears is carrying on as if nothing happened ... spotted doing everyday errands like she didn’t just cash in one of the most iconic catalogs in pop history.

The pop legend was seen deep in conversation on her phone while cruising in her Mercedes G63 AMG near her Thousand Oaks home in the L.A. area Thursday.

Rocking shades and casual clothes, Britney kept it low-key during the solo outing -- all just days after TMZ broke the news she sold the rights to her music.

BTW ... if you're eyeballing the ring she has on that finger ... a source tells TMZ, Britney is completely single -- she always wears rings on all her fingers!

As we reported, Britney sold her ownership stake to music publisher Primary Wave. The exact figure isn’t confirmed, but sources called it a "landmark deal," with estimates hovering around $200 million.