More than two million viewers tuned in to see Carol Vorderman and Des O'Connor bow out of Countdown.
The show, which aired last Friday, peaked at 2.1 million viewers with a 20% share of the audience, a spokeswoman for the show said.
The Channel 4 quiz usually averages at 1.7 million with an 18% average share.
In a message to viewers, Vorderman, who spent 26 years on the show, said today: "I was overwhelmed last week and deeply touched by thousands of messages of support and good wishes.
"It meant a great deal. Have a wonderful Christmas and thank you, one last time, for all of the years of pleasure and counting down.
"Duh duh, duh duh, duh duh duh duh, dong."