WASHINGTON — Regulators closed $3.5 billion-asset Frontier Bank in Everett, Wash., and three other smaller banks in the Midwest to bring the year’s failure total to 64.

On a night when the Federal Deposit Insurance Corp. also resolved three institutions in Puerto Rico, the four failures on the mainland added even more strain on the Deposit Insurance Fund. In addition to Frontier, the agency found buyers for $1.6 billion-asset CF Bancorp in Port Huron, Mich., $187 million-asset Champion Bank in Creve Coeur, Mo., and $67 million-asset BC National Banks in Butler, Mo.

In all, the seven failures Friday were estimated to cost the FDIC over $7 billion.

The agency said Union Bank in San Francisco will assume all of Frontier’s $3.1 billion in deposits, and acquire virtually all of its assets. The buyer and the FDIC will share losses on just over $3 billion of those assets. The failure was estimated to cost the FDIC $1.37 billion.

In the Michigan closure, First Michigan Bank in Troy agreed to assume all of CF Bancorp’s $1.4 billion in deposits, paying a 0.75% premium. First Michigan will also acquire $870 million of the failed bank’s assets, and share losses with the FDIC on $808 million of those assets. The failure was estimated to cost the agency $615 million.

The operations of Champion Bank will be transferred to BankLiberty in Liberty, Mo. The acquirer agreed to assume all of Champion’s $154 million in deposits without paying a premium, and purchase $153 million of the failed bank’s assets. BankLiberty and the FDIC will share losses on $113 million of those assets. The failure was estimated to cost about $53 million.

First Bank in Butler, Mo., agreed to assume all of BC National Banks’ $55 million in deposits without paying a premium. It will take over virtually all of the failed bank’s assets while sharing losses on $38 million of those assets with the FDIC. The failure was estimated to cost the agency $11 million.

Earlier in the evening, the FDIC announced three resolutions of Puerto Rican institutions: $12 billion-asset Westernbank Puerto Rico in Mayaguez, $6 billion R-G Premier Bank in Hato Rey and $2.5 billion-asset Eurobank in San Juan.