Armstrong Numbers

Instructions

An Armstrong number is a number that is the sum of its own digits each raised to the power of the number of digits.

For example:

• 9 is an Armstrong number, because 9 = 9^1 = 9
• 10 is not an Armstrong number, because 10 != 1^2 + 0^2 = 1
• 153 is an Armstrong number, because: 153 = 1^3 + 5^3 + 3^3 = 1 + 125 + 27 = 153
• 154 is not an Armstrong number, because: 154 != 1^3 + 5^3 + 4^3 = 1 + 125 + 64 = 190

Write some code to determine whether a number is an Armstrong number.

Bonus

Two optional tests are disabled by default. To enable them, add const TEST_BIG_INTEGERS = true to the global scope of your solution file (or uncomment the line provided in the stub).

These numbers exceed the default integer type, but 128-bit integers are sufficient to pass the tests; there is no need for BigInt.

---

Source

Wikipedia