This number is 4 divided by 2, which is a multiple of 4 and should be between 15 and 25.

4× 3+2 = 14 < 15 doesn't fit the question.

4×4+2= 18

4×5+2=22

4× 6+2 = 26 > 25 does not meet the meaning of the question.

The answer is18,22 people. Because it is a fill-in-the-blank question, you should write it all out.