Its a line of rubbish.
int polynom
Declares an integer called "polynom" and sets it's value to zero.
polynom &= 0xFFFF
Performs a logical AND between the current value of "polynom" and hexadecimal FFFF (sixteen bits, all '1's), and replaces the current value of "polynom" with the result.
I.e.
int polynom &= 0xFFFF;
declares in integer called "polynom" and sets it's value to zero - since 0 logically ANDed with anything gives zero by definition.