But even football couldn’t tackle CBS’ indomitable “NCIS,” which edged out the Seahawks-49ers clash to become the week’s most-watched show. It drew 19.6 million viewers, the Nielsen Co. said Thursday.

In third place was “NCIS: Los Angeles,” followed by the season finale of “The Voice.” The season finale of Fox’s singing competition “The X Factor” ranked 14th.

Among several Christmas specials, “A White House Christmas: First Families Remember” was the most-watched, ranking 20th place.

A preview airing of a new NBC sitcom, “1600 Penn,” ranked 23rd with 6.9 viewers. It premieres next month.

Overall for the week, NBC averaged 8.12 million viewers in prime time (4.9 rating, 8 share). CBS ranked second with 7.50 million viewers (4.9 rating, 8 share), while Fox had 5.64 million (3.3 rating, 6 share), ABC had 4.78 million (3.0 rating, 5 share), the CW had 1.43 million (.9 rating, 1 share) and Ion had 1.12 million (.8 rating, 1 share).

Among the Spanish-language networks, Univision led with an average of 3.21 million viewers (1.7 rating, 3 share). Telemundo had 1.24 million (0.6 rating, 1 share), TeleFutura had 740,000 (0.4 rating, 1 share), Estrella had 270,000 (0.1 rating, 0 share) and Azteca had 140,000 (0.1 rating, 0 share).

NBC’s “Nightly News” topped the evening newscasts with an average of 9.1 million viewers (6.1 household rating, 11 share). ABC’s “World News” was second with 7.9 million (5.3 rating, 10 share) and the “CBS Evening News” had 7.0 million viewers (4.6 rating, 9 share).

A ratings point represents 1,147,000 households, or 1 per cent of the nation’s estimated 114.7 million TV homes. The share is the percentage of in-use televisions tuned to a given show.

For the week of Dec. 17-23, the top 10 shows, their networks and viewerships: “NCIS,” CBS, 19.59 million; NFL Football: San Francisco at Seattle, NBC, 19.50 million; “NCIS: Los Angeles,” CBS, 15.48 million; “The Voice” (Tuesday), NBC, 14.13 million; “Sunday Night NFL Pre-Kick,” NBC, 13.67 million; “The Voice” (Monday), NBC, 13.37 million; “The Big Bang Theory,” CBS, 10.95 million; “The OT,” Fox, 10.94 million; “Mike & Molly,” CBS, 10.79 million; “Hawaii Five-0,” CBS, 10.54 million.

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ABC is owned by The Walt Disney Co. CBS is owned by CBS Corp. CW is a joint venture of Warner Bros. Entertainment and CBS Corp. Fox is a unit of News Corp. NBC and Telemundo are owned by Comcast Corp. ION Television is owned by ION Media Networks. TeleFutura is a division of Univision. Azteca America is a wholly owned subsidiary of TV Azteca S.A. de C.V.