Sum-Product Number

A sum-product number is a number $n$ such that the sum of $n$'s digits times the product of $n$'s digit is $n$ itself, for example

$$135=(1+3+5)(1\cdot 3\cdot 5).$$

The only sum-product numbers less than $10^7$ are 1, 135, and 144.

See also Amenable Number