NBC is celebrating its hot start to the 2013-14 TV season, announcing that it notched its highest premiere-week average prime-time rating in the key 18-49 demo in five years and beat its closest rival by the widest margin any broadcast net has racked up since 1997.

Based on Nielsen “live plus same day” figures for adults 18-49, NBC averaged a 3.1 rating, 9 share for the week, topping second-place ABC by 35%. It was the second year in a row that the Peacock Network won premiere week, posting year-to-year gains both times.

NBC reported that it finished No. 1 for the week not only in viewers 18-49, but in all other key demos among the big four networks. NBC was up 7% from a year ago in 18-49 and recorded its highest premiere-week rating since 2008.

NBC averaged 9.7 million total viewers for premiere-week prime to finish second behind CBS, which had 10.4 million.

NBC crunched the numbers from a variety of angles to come up with a long list achievements. Here are a few of the highlights:

• In total viewers, NBC notched its largest premiere-week audience (9.7 million) in six years.

• NBC leads the big four networks in every key demo — adults, men and women 18-34, 18-49 and 25-54.

• NBC’s "Sunday Night Football" is the No. 1 prime-time telecast of the week in the 18-49 demo and total viewers.

• NBC won the first two nights of the season in the 18-49 demo for the first time in 25 years.

• NBC became the first network in 19 years to post increases on the first four nights of the season in both the 18-49 demo and total viewers.

• NBC won Monday night by 74%, the biggest premiere-week Monday margin in People Meter history, with the premiere of "The Voice" up 21% from last year and "The Blacklist" claiming the best 10 p.m. drama rating on the big four broadcast nets in the past year.

• "The Blacklist" added 4.4 million total viewers in "live plus three day" results, the biggest increase ever for a broadcast program.

• NBC won Tuesday of premiere week in the 18-49 demo for the first time in eight years.