Project Euler: Problem 20

n! means n × (n − 1) × … × 3 × 2 × 1

For example, 10! = 10 × 9 × … × 3 × 2 × 1 = 3628800,
and the sum of the digits in the number 10! is 3 + 6 + 2 + 8 + 8 + 0 + 0 = 27.

Find the sum of the digits in the number 100!

int result = 0;
BigInteger temp = BigInteger.ONE;
 
for (long i=2; i<=100; i++) {
	temp = temp.multiply(BigInteger.valueOf(i));
}
String number = temp.toString();
for (int i=0; i<number.length(); i++) {
	result += Character.digit(number.charAt(i), 10);
}
System.out.println(result);

Lösung: 648