PE #20

Project Euler #20: Factorial Digit Sum description and solution in Java. A second follow up to my first post on my Aribtrary Precision Calculator, PowArray.

The problem statement is:

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!

Advertisements

PE #16

Project Euler #16: Power Digit Sum description and solution in Java. A follow up to my first post on my Aribtrary Precision Calculator, PowArray.

The problem statement is:

215 = 32768 and the sum of its digits is 3 + 2 + 7 + 6 + 8 = 26.

What is the sum of the digits of the number 21000?