Computation Workshop Solution Checker

Odd Digit Sums

Let \(N! = 1 \times 2 \times 3 \times \cdots \times N\). A positive integer is called valid if the sum of its digits is an odd number. For example \(131\) is valid because \(1+3+1=5\) and \(5\) is odd. For any positive integer \(x\) let \(v(x)\) denote the number of valid positive integers which are divisors of \(x\) (including \(1\) and \(x\) itself). For example \(v(100) = 6\) because \(100\) has \(6\) valid divisors: \(\{1, 5, 10, 25, 50, 100\}\).