How do I calculate offset from virtual address?
The page size indicates how much bits represent the offset in the physical frame. In this case you have pages of 4KB that means you need 12 bits because 2^12 = 4096. The offset in the physical frame always starts at the least significant bits. So for your example with
37064 = 0b1001 0000 1100 1000,

0000 1100 1000 = 200 in decimal is the offset in the physical frame. Since you have only one level of page tables, the rest of the bits to the left represent the actual physical page. You should not see it as a division even though it works. So the offset in the page table is 1001 = 9.