** Shares of Brazilian digital lender Nu Holdings NU.N rise 2.6% to $13.46 premarket

** Citigroup upgrades stock by two notches to "buy" from "sell"

** Citi analysts say Nu's earnings momentum to accelerate, citing operational tailwinds from Mexico and Colombia

** Raises PT to $18 from $9, representing a 37.2% upside to the stock's last close

** "Despite concerns on the macroeconomic environment...we see the recent quarters as a testament to the bank’s ability to not only navigate well but also accelerate in key portfolios while maintaining good asset quality" - Citigroup

** Nu Holdings posted a $637 million second-quarter net profit last week

** 11 of 16 brokerages rate the stock "buy" or higher, 4 "hold" and 1 "sell" or lower; their median PT is $15 - data compiled by LSEG

** As of last close, NU stock up 26.6% YTD

(Reporting by Kanchana Chakravarty in Bengaluru)

((Kanchana.Chakravarty@thomsonreuters.com))