An astronomical number of Millennium Tower Boston’s smaller units were sold to outside investors, while the entire building had more million-dollar sales last year than Back Bay and Beacon Hill combined, according to a new report.

“My own review suggested that an extraordinarily high percentage — maybe as much as 90% of residences sized under 821 square feet — were sold to investors,” Boston realtor David Bates said.

Bates has released a special report analyzing Millennium Tower’s first 425 sales. He points to a high number of investors, both foreign and domestic, which he determined through the Suffolk County Registry of Deeds. He deciphered a property was sold to an investor when it was not declared as a homestead or if it was bought with cash. Only 20% of Millennium Tower buyers have declared their residence a homestead, but the building’s developer does not see this as a sign of an empty building.

“We have a high degree of certainty our buyers live in our building. Just walk by it at night and look at all the lights on,” Millennium Partners managing partner Richard Baumert said. “Declaring something as your homestead is not indicative of whether you’re living there or not.”

The tower has drawn the attention of international buyers looking to enter the Boston market. As for the investors gobbling up all of the smaller units in Millennium Tower, Bates said they hail primarily from Asia. A San Francisco broker who markets luxury properties in Asia is reported to have sold 30 units in the building. Bingyi Chen, a Chinese immigrant living in Concord, has purchased an estimated 16 condos on behalf of investors back in China.

“We usually don’t comment on owner identities, but [Bates'] number seems pretty inflated,” Baumert said.

While he would not give further details, Baumert has said in the past that three-quarters of the owners of units in the building would actually live there. Dell founder and CEO Michael Dell purchased an $11M penthouse in the development toward the end of last year. Private equity billionaire John Grayken purchased the building’s Grand Penthouse for $35M, which was the largest condo sale in city history until the Four Seasons under construction on Dalton Street landed a $40M sale in recent weeks.

“In 2016, the tower had more $5M sales than the entire Boston condo market had in 2015,” Bates said. “Millennium Tower Boston also had a 45% market share of Boston's $2M condo sales in 2016.”

There were 345 million-dollar sales in the building last year, and the median sale price was $1.75M. A mere 27% of the total sales in the building were bought with debt — $256M of the $961M in total sales. Of the the 442 units in the entire building, only 11 remain up for grabs.

“It’s the most successful building in the history of the city,” Bates said. “When you see what they also did down the street at Millennium Place and are trying to do a few blocks up in Winthrop Square, they should just go ahead and rename Downtown Crossing ‘Millennium Crossing.’”