Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

Billionaire Warren Buffett gave Berkshire Hathaway stock worth $21.6 million away in the second half of 2012.

Buffett revealed the donations Monday. Buffett, who is Berkshire's chairman and CEO, made donations of Class B shares to four unnamed charities and three individuals between September and December.

The biggest single gift reported Monday was 172,375 shares worth $16.6 million given to a nonprofit.

These gifts are in addition to the 22.4 million Class B Berkshire shares Buffett gave to the Bill & Melinda Gates Foundation and the four Buffett family foundations that are slated to eventually distribute most of Buffett's fortune.

Buffett has said he plans to eventually donate all of his 350,000 Class A and 3.5 million Class B shares of Berkshire stock worth more than $51 billion to charities.