If A Number In One Of The Balloons is Included In The Answers To The Four Problems Below Then That Balloon Will Fly Away.
Answer or Solution : Balloons with a multiple of 9
The balloons with the multiples of 9 are 18, 45, 54, 63 and 99.
Square number balloons
Balloons with the Square numbers are 4, 16, 25 and 64.
Prime number balloons
The prime number balloons in the lists are 3, 7, 13, and 17.
So, the balloon left is 26