Earnings at the Trump International Hotel in Manhattan jumped 13 percent during the first quarter of 2018 — thanks to a late March visit by the crown prince of Saudi Arabia, whose entourage stayed there.

Prince Sanders, general manager of the Central Park West tower, credited the increased profits to “a last-minute visit to New York by the Crown Prince of Saudi Arabia,” in a May 15 letter obtained by the Washington Post.

Neither Crown Prince Mohammed bin Salman nor members of his royal family bunked at the president’s hotel because it didn’t have suites large enough to meet their demands, Sanders said.

But “due to our close industry relationships, we were able to accommodate many of the accompanying travelers,” he added.

The letter described a five-day visit in the final week of March that generated enough revenue to boost the hotel’s bottom line for the entire quarter, the paper reported.

And it revealed how little the public knows about the business that Trump’s company does with foreign officials.

The transaction and others like it — particularly at Trump’s hotel in Washington, a magnet for foreign government officials and domestic influence seekers alike — have caused good-government groups and other critics to charge that Trump is cashing in from governments seeking favorable relations or deals with the US.

Trump’s company has revealed little about the business it does with foreign customers — and the Democratic attorneys general of Maryland and DC have sued the Trump Organization for allegedly violating the Constitution’s emoluments clause, which bans presidents from using their office to line their pockets.

Neither the Trump Organization or the Saudi Embassy answered the paper’s questions about whether the Saudi government paid for anyone’s stay at the hotel.

Few foreign government officials who have stayed or staged events at Trump properties have been publicly identified — but the lawsuit, if successful, could reveal more details.

Last week, a federal judge in Maryland gave the go-ahead to the lawsuit alleging that by accepting government business at his properties, Trump was violating the constitutional clause.

“This was how the Framers protected against corruption,” Maryland Attorney General Brian Frosh, who filed the suit along with DC Attorney General Karl A. Racine, told the paper.

“They wanted to make sure the president would put the country above himself.”