Armstrong numbers

Also known as narcissistic numbers, Armstrong numbers are the sum of their own digits to the power of the number of digits. Confused? Here is an example:

153 = 1³ + 5³ + 3³

There are just four numbers, after unity, which are the sum of the cubes of their digits. 153 is one of them. Can you find out the other three?

Do write back to school@thehindu.co.in if you figure them out!