Not 16384 sectors, the docs clearly state that for a 64TB drive you need to set the sector size to 32768 ... 
The number of sectors is an unsigned 32 bit value, so the maximum value is 2^32 - 1, which is 4294967295. Multiply that by the sector size (32768, according to you and the docs), and you get 140737488322560, which is 128TB.
But that's irrelevant because you can't set the sector size. It's fixed at 512 bytes, which limits you to 2TB.
I'm pretty sure Piru mentioned this to you before...
