Paul Anka was only 16 when he composed and recorded "Diana" back in Ottawa in 1957, joining a growing group of teenage crooners of the era that included Bobby Darin, Jack Jones, Frankie Avalon and Neil Sedaka. The song has sold nearly 20 million copies and by one list -- Time magazine's -- is the second-biggest grossing record in history.

Now 49, he's become a rich man through his royalties from some 700 songs, appearances at Las Vegas and Atlantic City gambling palaces, real estate and bank holdings; a man with a private plane and extensive collections of art and wine.

So he really doesn't need his newest endeavor, acting, to keep bread on the table. But he's giving it a try, at his new agent's urging, and he's finding it fun.

This week, he turns up as Nick Angel in "Perry Mason: The Case of the Maligned Mobster" (Monday at 9 on NBC). Angel is not the title mobster -- Johnny Sorrento is, played by Michael Nader, a man charged with murdering his wife (Gwynyth Walsh).

Mason Adams plays Frank Halloran, Sorrento's personal lawyer, who has talked criminal lawyer Mason (Raymond Burr) into defending the mobster by swearing that Sorrento has been clean for a decade. But though Mason gets him off, he learns that there are other skeletons in his client's closet. And as if to prove that those who lie down with dogs get up with fleas, Mason also gets shot in this episode -- nevertheless appearing the very next day in the courtroom with his arm in a sling.

But it's that bit player, the middle-aged short guy who's thinning a bit on top, the one who takes a punch to the gut by an angry Sorrento, who's the new kid on the block.

"I really wanted the role badly," Anka said. "I apparently beat out a lot of people. It's a good, meaty role. He's a good guy/bad guy, and he has visions of being as important as Michael Nader's role."

And he doesn't get killed off, which leaves what Anka calls "a good possibility" that Nick Angel may resurface some day.

Anka sounds enthusiastic about acting, a career shelved during his earlier recording years.

"I went through all those young years and there wasn't really a place," he said. "I was kind of focused on my singing and writing."

But now he has a new agent who suggested that he might be ready to try a change of pace. The challenge: to fit acting around his other commitments.

"I've never been one to dabble in anything and all of a sudden I said, 'Yeah, maybe now it interests me.' So I'm studying with an acting teacher," he said. "But I've got to allocate my time now -- my time is pretty well dissected."

The Perry Mason show is by no means Anka's first acting venture. From September 1960 to January 1961, he guested on the pilot of "Dan Raven," an NBC police drama. Afterward, he showed up on a number of musical showcases including "Hollywood Spotlight" and "Hullabaloo" and programs hosted by Ed Sullivan, Danny Thomas, Perry Como, Dean Martin and Johnny Carson. When Carson took over "The Tonight Show" in 1962, Anka provided his theme song -- a composition that has been played more than 1.4 million times.

His score for the film "The Longest Day," in which he also appeared, earned him an Oscar nomination, and his theme song for Louis Malle's "Atlantic City" took first place at the Venice Film Festival. He owns 15 gold records for million-dollar sellers; four of his 22 BMI Songwriting Awards honor songs that have been performed more than a million times.

Anka's strong suit was always love songs, written for himself and for other crooners.

Before he was 18, Anka had written and recorded 20 top hits, including "You Are My Destiny," "Puppy Love," "Lonely Boy," and "Put Your Head on My Shoulder." But he also wrote "My Way" for Frank Sinatra, "She's a Lady" for Tom Jones, and "Times of Your Life," which Kodak uses as its theme song.

In 1974, Anka wrote "Having My Baby" for his wife, Anne de Zogheb. The parents of five daughters, 13 to 24, the Ankas mark their 28th wedding anniversary Saturday.

Despite his heavy schedule of personal appearances, "we're a very close family," he said. "We put a lot of focus on time together. We took all our summer vacations and all our winter vacations together. We went to Sun Valley, Idaho, and they all became very good skiers, and we were able to be in an environment that was indigenous to being a family."

The two eldest daughters -- Alexandra and Amanda -- have graduated from the University of Southern California; Alicia is a student at the University of Michigan and Anthea at Colorado. With only Amelia at home, the Ankas recently sold their 15-acre home in Carmel and moved to Pebble Beach, Calif., taking along their extensive art collection that includes pieces by Andy Warhol, Robert Rauschenberg and Frank Stella. Their inventory of wines includes a 1800 Rothschild bought for $15,000 in London.

Anka still travels half the year, appearing at Trump Castle in Atlantic City, the Riviera in Las Vegas and other nightspots and summer venues. The rest of the time, he's composing and recording and overseeing his business interests. He's also co-producing "Betcha," a game-show pilot for Viacom.

Anka has a new album due out this spring, and a record he's made with David Hasselhoff called "Freedom for the World" is already available in Germany. He's finishing a project with Michael Jackson and Sapphire, and he's preparing a new album for Frank Sinatra "if I ever get him in the studio."

He's also co-producing a release for Yukiko Haneda, a Japanese singer, for CBS/Sony, and doing a Christmas album with the Chieftains, an Irish group from Dublin, as well as a Christmas package of his own for RCA.

Next up: a role in a new Bruce Willis-Richard Gere film.