Print the missing primes
Jelly, 6 bytes in Jelly's codepage

½ÆRḟÆf


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Explanation:

½ÆRḟÆf
 ÆR    All primes less than or equal to
½      the square root of the input
   ḟ   but with the following removed:
    Æf All prime factors of {the input, by default}