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Composite prime (Posted on 2015-02-24) Difficulty: 1 of 5
What is the smallest prime number such that all of its digits are composite?

No Solution Yet Submitted by Math Man    
Rating: 5.0000 (1 votes)

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Solution | Comment 1 of 2
The composite digits are 4, 6, 8 and 9.
Clearly the number must have 2 or more digits so must end in 1, 3, 7, or 9.
Since 9 is the only composite, it must end in 9.
Checking 2 digit numbers with a composite first digit:
49 not prime
69 not prime 
89 is PRIME

  Posted by Jer on 2015-02-24 08:29:41
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