@extra-number/divisor-sum (npm): Sum divisors of number.
Keywords: extra|number|standard|utility|method|manipulation|function|merferry|divisor|sum|aliquot-sum|arithmetic-mean|binomial|ceil|ceil-div|compare|constrain|cubic-mean|degrees|factorial|floor|floor-div|gcd|geometric-mean|harmonic-mean|is|is-pow|is-prime