Talk:Primes whose sum of digits is 25: Difference between revisions
Talk:Primes whose sum of digits is 25 (view source)
Revision as of 16:59, 21 March 2021
, 3 years ago→The limit of primes that do not contain zeroes: added 8 billion year estimate for +2 approach
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: I think it is possible to put an upper limit on primes whose digits sum to 25 and have no zeroes in them. The largest number with no internal zeros and a digit sum of 25 would be 1111111111111111111111111 (25 digits). --[[User:Tigerofdarkness|Tigerofdarkness]] ([[User talk:Tigerofdarkness|talk]]) 10:54, 21 March 2021 (UTC)
: Correct, stretch goal updated. If zeroes were allowed there would be an infinite number of them. It will need reasonably decent bignum handling and a fast prime number checker. I expect this is not really do-able in asm, C, etc. I would put a reasonable (soft) upper limit of say 30 mins runtime on this and not be too critical of anything around that. The Phix algorithm generates 1.65e7 potential candidates (without testing for primality that takes just 7.7s) as opposed to +2 (it is rather daft to test even numbers for primality!) generating 5.55e24 candidates which at that same (test-less) rate would take around 8 billion years. --[[User:Petelomax|Pete Lomax]] ([[User talk:Petelomax|talk]]) 12:34, 21 March 2021 (UTC)
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