bitwise operations.
241294492511762325 >> 46 means shift the binary form of number which is
0000001101011001010000000001000000000000011010111111011110010101
to the right 46 spaces while replacing with 0s 0000000000000000000000000000000000000000000000000000110101100101
0xFFFF is hex version of 1111111111111111 (note two missing bits he reserved for gold :D )& 0xFFFF is doing a AND operation of the bits.
0000110101100101
1111111111111111
----------------
0000110101100101
so 0000110101100101 in decimal is 3429