There are 11 letters. Those have 11! Different arrangements. However, there are 4 "s", 4 "I", and 2 "p" letters that are indistinguishable from other letters of the same type. This reduces the total of different arrangements by a factor of (4!*4!*2!). That leaves (11!)/((4!)(4!)(2!)) = 34,650 different arrangements.
