This number is a prime.
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The number of composites between each of the successive primes after the 3191-th prime are the digits of 3191 read left-to-right. E.g., The 3191-th prime is 29383; and 29383 (3) 29387 (1) 29389 (9) 29399 (1) 29401. No larger example is known. [Gaydos]