323. To steal Kevin Lombardo's explanation:

"The answer is:

323

The numbers are products of consecutive prime numbers.

2 x 3 = 6

3 x 5 = 15

5 x 7 = 35

7 x 11 = 77

11 x 13 = 143

13 x 17 = 221

17 x 19 = 323"

And yes, 2 is a prime number, and 1 is not. Many people have that the other way around. 2 is the only even prime number.

Winner: Michelle Nichols

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