Find the missing number?

The missing number is $\boxed{31}$.

The numbers in the sequence are all prime numbers, except for the missing number. The missing number must be a prime number that is less than 34, since 34 is the next prime number in the sequence. The only prime number that is less than 34 and is not in the sequence is 31. Therefore, the missing number is 31.

Here is a list of all the prime numbers less than 34:

• 2
• 3
• 5
• 7
• 11
• 13
• 17
• 19
• 23
• 29
• 31

As you can see, 31 is the only prime number in this list that is not in the sequence. Therefore, the missing number is 31.