Create a chain of consecutive digits starting with 1 and following 9 by 0:
123456789012345...How many digits are needed to obtain the 1st prime number?
(In reply to
re: computer exploration by Ady TZIDON)
I had already determined that the possible candidate(s) would end in 1 or 7:
The digital root of a prime number, but for 3, is never a multiple of 3. A prime number, but for 2, never ends in an even number.
The digital root of the chained number is a multiple of 3 except
when the number ends in 1, 4, or 7, in which case the digital root is 1. Thus, the chained number, if prime, ends either in a 1 or 7.
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Posted by Dej Mar
on 2015-04-11 00:23:31 |
re(2): computer exploration
