Cute. He could be full Sibe. He could be a very Sibe looking mix. Do you have a reason to believe one way or the other?
If he was sold with AKC registration papers, and you have reason to doubt his parentage, you need to contact the AKC.
He wasn't sold with AKC papers, but I did see his parents and they look like huskies. Personally, I don't care if he's a full or a mix. I love him either way. It's just tiring when other's question it because of his coloring(or lack of), ear shape/size, floppy ear, etc.
I ran into someone with a puppy maybe 2-3 weeks older than him and she had a slimmer head shape, body and much bigger ears and the owner was set on him being a mix; Malamute or Shepherd.