An Armstrong number is a number that is equal to the sum of its own digits each raised to the power of the number of digits. For example, 371 is an Armstrong number since 3^3 + 7^3 + 1^3 = 371. Armstrong numbers are also known as narcissistic numbers. To determine whether a given number is an Armstrong number, we can write a program that computes the sum of the digits raised to the power of the number of digits, and then compare it to the original number. If they are equal, then the number is an Armstrong number.