The Millennium Tower Boston’s 60th-story penthouse unit, which had been listed for $37.5 million, has been placed under agreement as a “family residence,” developer Millennium Partners said today.

The 13,000-square-foot luxury residence atop the 625-foot-tall skyscraper in Downtown Crossing is one of 442 condominiums in the city’s newest landmark. The remaining units are available for prices starting at $3.3 million, according to Millennium Partners. Smaller units on the lower levels sold for as low as $850,000.

The penthouse unit occupies the entire top floor and has a 2,000-square-foot outdoor terrace.

Millennium Partners sold out more than 90 percent of the condos in 11 months, with sales topping $900 million, more than a year before the anticipated opening this summer. The complex contains the city’s largest private fitness center at 10,000 square feet and high-end amenities including as two restaurants.