901

This number is a composite.

The only three-digit composite number (901 = 17*53) with a middle zero that gives only primes (9001, 90001, 900001), when up to three zeros are added in the middle.

Every number of the form (9+17n)01 (n an integer) has partial or complete prime factorization 17*n53. E.g., 4301 = 17*253 = 11*17*23, 6001 = 17*353, 9401 = 17*553 = 7*17*79, 101201 = 17*5953.