perplexus.info :: Numbers : Minimal Primes

Minimal Primes (Posted on 2012-04-24)

409 is an interesting prime number. If you remove any number of its digits, then you will get a number that is not prime.

4=2^2
0=not prime
9=3^2
40=2^3*5
49=7^2
09=9=3^2

Call a number with this property a minimal prime. Find all minimal primes.

Submitted by Math Man

Rating: 4.6667 (3 votes)

Solution: (Hide)

2, 3, 5, 7, 11, 19, 41, 61, 89, 409, 449, 499, 881, 991, 6469, 6949, 9001, 9049, 9649, 9949, 60649, 666649, 946669, 60000049, 66000049, 66600049

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
re: of course it also inspires a computer program	Charlie	2012-04-24 17:28:34
re: solution	Math Man	2012-04-24 17:26:45
of course it also inspires a computer program	Charlie	2012-04-24 16:50:53
solution	Charlie	2012-04-24 16:17:04
spoiler	Ady TZIDON	2012-04-24 10:37:58

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