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Composite prime (Posted on 2015-02-24)

What is the smallest prime number such that all of its digits are composite?

See The Solution 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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