WASHINGTON (AP) -- Furloughing federal workers in last month's partial federal shutdown cost the government 6.6 million workdays, according to a White House budget office report Thursday.

Taxpayers will cover the $2 billion cost of providing back pay to the 850,000 workers sent home during all or part of the 16-day shutdown. After Congress decided in the middle of the shutdown to pay Pentagon workers, and recall them to work, 400,000 federal employees were kept off the job. At the peak, about 850,000 individuals per day were furloughed, according to the Office of Management and Budget.

The Obama administration has said the shutdown and uncertainty over raising the government's borrowing cap will curb economic growth in this quarter and may have meant that 120,000 fewer private sector jobs were created in early October.

The budget office says closing national parks cost communities $500 million in lost spending by visitors, while the Internal Revenue Service delayed $4 billion in tax refunds and will have to put off next year's filing season by up to two weeks.

The effects of the shutdown were felt across the country, from a three- or four-day delay in Alaska's crab fishing season, as well as delayed oil drilling permits in North Dakota, Wyoming and Utah. Home loan decisions were delayed for 8,000 applicants under a Department of Agriculture loan guarantee program.

Small business contracts with the Pentagon dropped by almost one-third. The Bureau of Alcohol, Tobacco and Firearms was unable to issue export certificates for beer, wine and distilled spirits. The Small Business Administration and Federal housing Administration were unable to issue loans during the shutdown. Hundreds of people were unable to enroll in clinical trials at the National Institutes of Health.

U.S. Geological Service field testing of a new technology to prevent the spread of the Asian carp, an invasive species, into the Great Lakes will have to be delayed for six months because the agency missed a narrow window for the tests due to cooling water temperatures. Important government reports on the economy were delayed as well.

"The report makes clear that the costs and impacts of the shutdown were significant and widespread, and demonstrates why this type of self-inflicted wound should not occur again," said White House budget director Sylvia Mathews Burwell.