Sum of the digits of 1729!

Computer Science Level 3

Find the sum of digits of the decimal representation of 1 × 2 × ⋯ × 1729 1\times2\times\cdots \times1729 .


The answer is 19863.

Rishabh Deep Singh by Rishabh Deep Singh , 23, India

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1 solution 

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import java.math.BigInteger;

public class main {
    public static void main( String[] args) {
        BigInteger sum = BigInteger.valueOf(0);
        BigInteger fact = BigInteger.valueOf(1729);
        BigInteger temp = BigInteger.valueOf(0);
        for (int i = 1729; i > 1; i--) {
            fact = fact.multiply(BigInteger.valueOf(i));
        }
        while (!fact.equals(BigInteger.ZERO)){
            sum = sum.add(fact.mod(BigInteger.valueOf(10)));
            fact = fact.divide(BigInteger.valueOf(10));
            System.out.println(sum + " "+ fact);
        }
         System.out.println(sum);
    }
}

I hope no can is going to solve this using Mathematics

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