Only Danica McKellar (search), the girl who played Winnie Cooper (search) on the beloved drama "The Wonder Years" (search) and a real-life math genius, could make numbers and terms like "statistical mechanics" sound sexy.

"Math is hard, but that doesn't mean it's not worth it," McKellar told the Post. "The rewards I think are really great. I used to call them [getting] 'Math High' — the feeling that comes when you solve a problem and you get filled with adrenaline. It feels great and you go, 'Oh yeah!' "

After years away from TV, McKellar, 30, has been turning up on major network shows all over the dial. It began in 2002, when she landed a recurring role on the "West Wing" — but now she is popping up on a new series nearly every week.

Just last week she co-starred on "Navy NCIS." This week she appears on the WB's critically acclaimed "Jack & Bobby" as a college student, and next month, she has a major guest-starring role — as the sister of a murdered prostitute — on the much talked-about series finale of "NYPD Blue."

McKellar is also the star of an upcoming movie on SCI FI called "Stratosphere," in which she plays a brainy reporter trying to save the world.

"I try to do a little bit of variety, but generally speaking, I'm gonna end up playing roles of people who are generally smart and good natured," she says.

You want smart? In college, McKellar co-authored a proof — new research proving an original math principle — that was published in a prestigious British physics journal. Now, the complicated mathematical theorem is named after her and its co-authors.

And don't even mention the Web site where McKellar answers tricky math problems for fans (danicamckellar.com).

"Acting and doing math are completely opposite," she says. "But math at a certain level really is creative."

After "The Wonder Years" ended its five-year run in 1993, McKellar headed to UCLA, planning to major in film. But, she says, she missed "the way my brain felt when I was doing math.

"I missed that clear headedness that you get when you spend a lot of time working on problem solving."

She ended up with a degree in math and spent several years away from the hustle of the entertainment industry, where she had worked since the age of 10.

"I took a break," she says. "I joined a sorority. I got involved around campus. I ended up joining a Shakespeare group because I was missing acting — and there was this amazing feeling that, when I was told about an exam or a function, I could commit to it. I knew I was going to be there and it was a completely new feeling for me."

McKellar lives in Los Angeles now and has a serious boyfriend but no plans to get married anytime soon, she says.

"This business doesn't really lend itself to the whole family thing," she says. "If I decide to have a family at some point, I want to be there for my kids. I don't want to pass that along to somebody else."