数字的乘积作为一位数字

I am trying to compute the product of non-zero digits, until the result is a single-digit number. For example, the number 512983 is 2, because 5×1×2×9×8×3 = 2160 and 2×1×6 = 12 (note the omission of the zero digit) and 1 × 2 = 2. But every time I run this I only get 0 I am trying to compute the product of non-zero