WASHINGTON — Over 600,000 people signed up for a plan through Obamacare’s federal exchange in its first four days of open enrollment, significantly outpacing last year’s sign-ups, according to official figures released Thursday.

The Centers on Medicare and Medicaid Services (CMS) said that 464,140 customers renewed their coverage while another 137,322 customers were new enrollees, for a total of 601,462. The number only includes people who signed up through the HealthCare.gov portal, which services 39 states.

By comparison, some 1,008,281 customers signed up through Healthcare.gov in the first 12 days of enrollment in 2016, the first period for which data is available. While not a perfect comparison, the daily rate of sign-ups is significantly faster this year: 150,366 per day in 2017, compared with 84,018 in 2016.