President Barack Obama -- Simon Cowell's Got Nothing On Me ... Launches Philly Singing Group's Career

15 seconds of singing for President Obama -- and making him clap and dance -- is all it took for a small time Philly R&B group to start blowing up ... and score a gig with the Philadelphia 76ers.

The group of 5 guys, ages 17-20, is called Brotherly Love, and they performed at a rally Obama attended for Pennsylvania gubernatorial candidate Tom Wolf over the weekend.

Afterward the group was supposed to pose for a pic with the prez, but instead used their time to bust out a song for him. You gotta watch the video ... Barack was definitely feeling it.

Brotherly Love posted the video, and now their rep tells us they're getting a slew of offers ... including the chance to sing the National Anthem before a 76ers game.