We know ,
File size using double indirect pointer = ( Disk block size / Disk block address )2 * ( Disk block size )
==> (Disk block address)2 = ( Disk block size )3 / File size
==> (Disk block address)2 = 239 B / 235 B
==> (Disk block address)2 = 16 B
==> Disk block address = 4 B = 32 bits
So we need 32 bits addresses for the desired purpose..