Talk:Titanic Prime consisting of 111 Blocks of each Digit plus Zeroes

Yep, I am 90% sure this is not prime: $397$ is a factor.

The expression I used is:

((10^111-1)/9*(10^888 + 2*10^777 + 3*10^666 + 4*10^555 + 5*10^444 + 6*10^333 + 7*10^222 + 8*10^111 + 9))*10^x+1

Replace x with the number of zeroes + 1.

For $1 \le x < 5000$, I have found 3 primes. (took around 2 hours)

They have $399, 1667$ and $1917$ zeros respectively.

I doubt it is a typo this time. --RandomUndergrad (talk) 15:30, 6 March 2022 (UTC)

Right okay, I *really* need to do some research on this to find out what the sources say. I will take some time to do that but probably not today. --prime mover (talk) 16:08, 6 March 2022 (UTC)

Actually it's rather a basic-comprehension-of-arithmetic error.

This is how the prime is described on the Harvey Dubner list on Prime Pages (get to it from https://primes.utm.edu/bios/page.php?id=5 ):

$123456789 · (R(999)/R(9)) · 10^{2285} + 1$

which is $(123456789)_{111} (0)_{2284} 1$ and not in any way $\paren 1_{111} \paren 2_{111} \paren 3_{111} \paren 4_{111} \paren 5_{111} \paren 6_{111} \paren 7_{111} \paren 8_{111} \paren 9_{111} \paren 0_{2284} 1$.

As for $123456789 · (R(999)/R(9)) · 10^{2285} + 1$:

It was checked that it is a prime number using the "Alpertron" Integer factorisation calculator on $6$th March $2022$.

This took approximately $50.2$ seconds.

Again, an errata page is needed. I am wondering whether to get in touch with David Wells (he lives not far from me) but I doubt he'd be impressed to learn his most influential work has $175$ mistakes in it. --prime mover (talk) 16:50, 6 March 2022 (UTC)

Completely forgot the Prime Pages have pages for the discoverers of big primes, listing their discoveries.

Then we should be fine after the title of this page is changed slightly. --RandomUndergrad (talk) 17:47, 6 March 2022 (UTC)

job done --prime mover (talk) 20:34, 6 March 2022 (UTC)