Get thee behind me Satan-Prime! Satan-Primes
who are they?
they are Primes containing 666
these are Satan-Primes:[46663,266677,666599,666683,616669]
these are NOT :[462667,665669,36363631,555]
Plot
Every number bigger than 6661 has Satan-Primes behind him
The Challenge
Given an integer n&gt;6661 find the Satan-Prime behind (or equal) and closest to itself.
Examples
Integer n=30000 has 3 Satan-Primes(SP) behind it:[6661, 16661, 26669].
Your code must return 26669 which is the closest behind it
Test Cases
Input-&gt;Output
6662-&gt;6661    
10000-&gt;6661    
66697-&gt;66697 (a SP returns himself)  
328765-&gt;326663  
678987-&gt;676661
969696-&gt;966677

Rules
Yor code should work for any n in the range of your language.
This is code-golf, so the shortest answer in bytes wins!
Neim, 9 bytes

&gt;ͻ:D+6S÷


Explanation:

&gt;         Increment input
 ͻ        Start infinite loop
  :        Previous prime
   D       Duplicate
    +6     Push 666
      S    Swap
          See if 666 is a substring of the top of the stack
        ÷  If true, break


Try it online!