This election saw the highest turnout of any federal general election recorded by EAVS to date with 67.7% of the citizen voting age population casting ballots that were counted.
More than 209 million people were active registered voters for the 2020 general election and more than 161 million voters cast ballots that were counted for this election.
The US Election Commission has these numbers
209 million registered 161 million votes.
https://www.eac.gov/news/2021/08/16/us-election-assistance-commission-releases-2020-election-administration-and-voting