One day our teacher asked us a puzzling question:

There is a 2-digit number with 2 different digits which has a special property. When the sum of its digits is added to the product of its digits the result is the number itself. What is this special number?

[For example, take 24. The sum of its digits is 6 (2 + 4). The product of its digits is 8 (2 x 4). But 6 + 8 is not 24 - because 24 is not the special number.]