Calculate the value of \$\zeta(s)\$
Mathematica, 9 7 11 bytes

Zeta@#~N~6&amp;


Explanation:

Zeta@#       (* Zeta performed on input *)
      ~N     (* Piped into the N function *)
        ~6   (* With 6 digits (5 decimals) *)
          &amp;  (* Make into function *)




Without builtin:

Mathematica, 23 UTF-8 bytes

Sum[1/n^#,{n,∞}]~N~6&amp;


Thanks to Kelly Lowder