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Old 2020-09-01, 05:31   #1
Sep 2019

23 Posts
Default Smallest composite without known factors "stuck" on (10^79-181)%(10^79-1)/9

The "Smallest composite without known factors" on the status page often points to, but that number is actually prime.

Is it possible to fix that entry so that we can see the real smallest unfactored number?
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Old 2020-09-01, 09:21   #2
kruoli's Avatar
Sep 2017
Porta Westfalica, DE

2×13×19 Posts

It thinks that 1551548344191988309623860115843108935500421 is a factor of that number for some reason. Maybe it thinks it is composite because it evaluates the expression to 1111111111111111111111111111111111111111111111111111111111111111111111111110931 and not 1111111111111111111111111111111111111111111111111111111111111111111111111111091?
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Old 2020-09-01, 09:28   #3
retina's Avatar
"The unspeakable one"
Jun 2006
My evil lair

22·5·307 Posts

There is a duplicate entry:
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Old 2020-09-01, 11:43   #4
JeppeSN's Avatar
Jan 2016

23×3×7 Posts

There must be or have been some inconsistence on how the precedence is when the parentheses are not explicit.

If you type (10^79-181)%((10^79-1)/9) you come to the fully factored 79-digit composite number:

If you type ((10^79-181)%(10^79-1))/9 you come to the 79-digit prime:

Both these entries are entirely correct.

However, the entry you link:
seems to be a mix-up of the two interpretations. It has evaluated to "C" (composite). But when you click Show digits, you see the expansion for the 79-digit prime.

I speculate that one piece of code in factordb sees the expression in one way, and another place sees it in the other way, and we have this mix-up. The schizophrenic entry needs to be removed, and (if not fixed already) the operator precedence convention must be consequent.

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