What is the smallest whole number that is equal to seven times the sum of its digits? Good Luck

21.

Explanation:

The two-digit number ab stands for 10a + b since the first digit represents 10s and the second represents units. If 10a + b = 7(a + b), then 10a + b = 7a + 7b, and so 3a = 6b, or, more simply, a = 2b. That is, the second digit must be twice the first. The smallest such number is 21.

These are the multiples of 15 but what you are probably asking or what are the factors of 15