The Columbia Records boss, who produced five tracks on the album, insisted that Adele's campaign for 21 is still only in its early stages.
Adele topped the US Hot 100 singles chart for a seventh week with the album's lead single 'Rolling In The Deep' on Thursday, delaying the release of her second US single 'Someone Like You'.
"Really, we are just on our first single and we think there are probably five, so I think it's just the beginning," Rubin told Billboard of the star's US campaign.
"And she's barely toured at all, so really it's in the baby stages. I think it's a beautiful album that we're all really proud of, and it's amazing that it's connecting with people in the way that it is and we just hope it continues to do so."
Rubin also credited Adele's voice and songwriting ability as the core selling point that has seen the album shift over 7 million copies worldwide since its release earlier this year.
"She is an incredible singer. She bares her soul in her songwriting, and it's the real thing... She uses her vocal instrument in a way that we don't get to hear a lot.
"What she is doing, it's a very pure expression of herself and it resonates with people. There is no trickery involved. It's a really honest album."
Adele recently announced her rescheduled US tour dates after cancelling a string of gigs earlier this month when she contracted acute laryngitis.
Meanwhile, the singer will release her third UK single 'Set Fire to the Rain' on July 3.
Watch Adele perform 'Someone Like You' below: