The number 153 belongs to a special class of numbers that are equal to the sum of powers of their digits. In other words, these are n-digit numbers that equal the sum of the nᵗʰ powers of their own digits.
For example,
153 = 1³ + 5³ + 3³
Such numbers are known by various names—narcissistic numbers, Armstrong numbers, “numbers in love with themselves,” or perfect digital invariants. These remarkable numbers have fascinated number theorists for decades.