No he is not an Arrancar. Because if it was that easy, there would be more arrancar. I'm sure becoming a hybrid will bring you near death first...since its like such a huge deal (ie when ichigo became a vaizard)
He wasn't in Soul Society because.....
1. he's a hollow
2. he was destroyed
Aizen is gangsta for making everyone wear white.
Tousen: "So what are we going to wear anyway? how do we tell each other apart from the shinigami?"
Aizen: "I GOT IT....lets wear exactly what they wear...but make it WHITE!"
Ichimaru: "OH SH*T, now THATS gangsta!"
Tousen: "....even I wouldn't say that..."
Aizen: "Loosen up Tousen...check this out...lets show him Gin!"
Tousen: "... 0_0 ..."