* 23.9 million Americans watch NFL season kickoff
* Democratic convention draws 25.1 million
By Jill Serjeant
LOS ANGELES, Sept 6 (Reuters) - Former President Bill Clinton beat strong competition from football to win the most TV viewers with a speech at the Democratic National Convention that also sparked more than 22,000 tweets per minute.
According to final data from Nielsen, it was a close race for the TV audience, with an average 23.9 million viewers watching the National Football League's season kickoff game on NBC between the Dallas Cowboys and the New York Giants on Wednesday night.
Nielsen said an estimated 25.1 million viewers across seven cable and broadcast networks watched the second night of the convention in prime time, when Clinton delivered a lengthy, humorous and detail-heavy defense of President Barack Obama's first term in office.
The total figure however was down from the 26.2 million TV audience for first lady Michelle Obama on Tuesday night.
On social media, Clinton fired up the Twitterverse, making hashtags like #arithmetic, #bill and #billclinton among the top trends in the United States on Wednesday evening.
Arithmetic also swiftly became a popular word in media and blog headlines after Clinton said: "People ask me all the time how we delivered four surplus budgets. What new ideas did we bring? I always give a one-word answer: arithmetic."
"Bill Clinton: Our Arithmetic Teacher" ran the headline in a blog on MinnPost.com in Minneapolis. Comedy Central's satirical Indecisionforever.com website ran a piece called "The Arithmetic of Bill Clinton's Speech" and the NationalReview.com website posted a column "Analyzing the Clinton-Obama 'Arithmetic.'"
According to Twitter, Clinton racked up 22,087 tweets per minute - below the 28,000 seen for Michelle Obama during her address in Charlotte, North Carolina on Tuesday, but beating Republican presidential candidate Mitt Romney's 14,289 tweets per minute last week by a large margin.
Clinton's Twindex score, which measures how Twitter users feel about a political person on a scale of 1 to 100, rose from 59 to 70 immediately after his 49-minute address.
On cable news networks, Clinton's speech - which ran well past the 10 to 11 p.m. ET prime time hour - polarized political pundits as deeply as his two terms as president had done in the 1990s.
Fox News Channel's senior political analyst, Brit Hume, said Clinton was "the most talented politician I've ever met." But Hume took issue with the speech, calling it 30 percent too long, "a little self-indulgent" and so packed with facts that it may have turned off the average American TV viewer.
On CNN, political analyst David Gergen said Clinton had been "the best political orator in the country" for the past 20 years.
"Wednesday's talk was the best and most influential he has given since leaving the White House a dozen years ago," Gergen added.