DivisorSigma

DivisorSigma[k, n] gives the divisor function σk(n), the sum of the k-th powers of divisors of n.

Examples

Sum of divisors (k=1):

DivisorSigma[1, 12]
(* 28 *)

Number of divisors (k=0):

DivisorSigma[0, 12]
(* 6 *)

Sum of squares of divisors:

DivisorSigma[2, 6]
(* 50 *)

Please visit the official Wolfram Language Reference for more details.