Find the next number in the series 13, 17, 19, 23, 29, _.

The given series appears to be a series of prime numbers.

Prime numbers are numbers that have only two factors: 1 and the number itself. The factors of 13 are 1 and 13, the factors of 17 are 1 and 17, the factors of 19 are 1 and 19, the factors of 23 are 1 and 23, and the factors of 29 are 1 and 29.

The next prime number after 29 is 31.

So, the next number in the series 13, 17, 19, 23, 29, _ should be 31.