They had bribery down to a business.

A federal prosecutor Tuesday told jurors during closing statements in the bribery case against former Nassau County Executive Ed Mangano that his relationship with corrupt businessman Harendra Singh was “not a friendship.”

“This is a business,’’ prosecutor Raymond Tierney said.

Mangano is accused of helping Singh land loans in exchange for things such as a lucrative no-show job for Mangano’s wife, Linda and a $7,000 Panerai watch for son Sal.

Mangano’s lawyer fired back in his closings that “Harendra Singh probably told 400 lies on the stand.”