Check If my String is Prime
Jelly, 4 bytes
OÆPẠ

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Explanation
Remember that a string is an array of characters, so operations like O will apply to each individual character.
OÆPẠ
O        Ord; cast each character to a number
 ÆP      Is it ÆPrime? gives 1 for truthy and 0 for falsey
   Ạ     Ạll; returns 1 if the array contains no falsey values