Onitakae

I don't know..I guess primes would cut it although I think it wouldn't be the right one.. All of these were easy until I got to this one...

Honestly, it's my brother's 5th grade math homework. Yup- go figure...

Please help, I've spent about a good hour with my family thinking about this. I'd really like to get an answer because this question's killing me. If you guys have any clue what might be an answer, I'd greatly appreciate it.

Alrighty, what do all these numbers have in common?? 3,217 5,153 2,189 362 482 177 5,408 Please hurry