21. Lazy Sheep told Pretty Sheep the unit digit of a three-digit number, and told Happy Sheep the tens digit, and told them that the sum of the digits of this three-digit number is 12.
Pretty Sheep said: “I don't know what this number is, but it must be a multiple of 5.” After hearing Pretty Sheep's words, Happy Sheep said: “I know what this three-digit number is, and it is a multiple of 4.”
What is this three-digit number? $\qquad$
$480$