Square Inc.

Square (SQ - Get Report) shares on Friday advanced for a fourth day after a Citi analyst reiterated a buy rating on the mobile and online payment processor. 

The stock was trading 3.5% higher at $82.24 on Friday after Citi analyst Peter Christiansen cited "improving momentum" at Square.

On Tuesday a Raymond James analyst, John Davis, had upgraded the stock to market perform. That upgrade was particularly notable since Davis had gone bearish on Square in January, lowering the stock to underperform.

Both the Citi and Raymond James analysts praised Square's business debit card, pointing to growing sales and growth potential.

The San Francisco company is also making good on pledges to speed product development, Christiansen said, citing 32 new products and features so far in 2019.

Square has seen one increase and one cut in analysts' earnings estimates in the past few weeks, Zacks Investment Research notes. 

"The recent price action is encouraging, though, so make sure to keep a close watch on this firm in the near future," Zacks wrote.

Square shares closed at $73.43 on Monday. In the four trading days since then, the stock is up 12%.