Top General Motors Co. executives collectively acquired millions of dollars in company stock in the first week after shares returned to public trading with the richest debut in U.S. history.

GM CEO Dan Akerson purchased 15,000 shares valued at $503,094. Appointed to GM’s board of directors after the auto maker exited bankruptcy some 16 months ago, Akerson took over as CEO from Chairman Ed Whitacre on Sept. 1 to direct a road show leading to the $21.2 billion initial public offering.

Akerson, 61, will become chairman of GM at the end of the year, when Whitacre retires completely. A former private equity executive, Akerson was awarded a pay package earlier this year valued at $9 million.

Whitacre, who will receive total compensation this year also of $9 million, purchased shares valued at $554,158.

GM Vice Chairman and Chief Financial Officer Chris Liddell, hired away from Microsoft Corp. last year to fix GM’s finance department, purchased stock worth $26,400.

A number of additional GM executives and officers, including vice chairmen Stephen Girskey and Tom Stephens, also acquired shares valued at $26,400, according to a filing earlier today with the Securities and Exchange Commission.

GM’s IPO last week reduced the U.S. Treasury’s stake to 33% from 61%, earning taxpayers just over $11 billion. The Treasury used some $50 billion in taxpayer funds to usher GM through bankruptcy and its subsequent restructuring.