They got this beast’s number.

A convicted killer on El Salvador’s list of most-wanted gang members has been arrested while living illegally in the US, according to the feds — with his mugshot showing “666” tattooed across his forehead.

Antonio Israel Lazo-Quintanilla was arrested last month in Maryland for driving without a license — but is wanted in his home country for a slew of terrifying felonies, including extortion, drug possession and aggravated homicide, the Department of Homeland Security (DHS) said Monday.

The illegal immigrant — who has other tattoos covering the rest of his face under the giant “666” — is also “a confirmed member of the 18th Street Gang, a Foreign Terrorist Organization,” and was on El Salvador’s most-wanted gang members list, the department said in a statement.

“This gang member on El Salvador’s most wanted list is a perfect example of ICE targeting the worst of the worst,” DHS Assistant Secretary Tricia McLaughlin said.

“He may lack a violent rap sheet in the US but this criminal illegal alien is clearly a public safety threat.”

His arrest was proof that “ICE is arresting criminal illegal aliens BEFORE they can victimize Americans,” McLaughlin said.

It was not immediately clear when the gangbanger came to the US, but he had been living here unlawfully for some time, officials said.

The 18th Street Gang, also known as Barrio 18, is one of Central America’s largest and most violent criminal networks.

Around 70% of ICE arrests involve illegal aliens who have been charged with or convicted of a crime in the US, but that figure does not include gang members, terrorists, or fugitives who carried out their crimes abroad, the statement said.

ICE agents have arrested nearly 500,000 illegal aliens nationwide this year, with most facing criminal charges or prior convictions, McLaughlin said.

Lazo-Quintanilla remains in federal custody pending deportation and possible extradition to El Salvador, where he faces long-standing felony warrants, according to the DHS.