Monday, March 16, 2026

Some recent large emirps

Let it be understood that all emirps come in pairs, say (p, q) where the number of (decimal) integer digits of p and of q are identical, but p < q. Since, in the following, we are dealing with record large integers, I will explicitly state the value of q, the larger of the pair, followed by a linked p in square brackets.

In 2007, Jens Kruse Andersen noted the 10007-digit 10^10006+941992101*10^4999+1 [p] as the then-largest-known emirp. Eighteen years later, Stephan Schöler managed to up this by four decimal digits with his 3867632931*10^10001+1 [p]. One month ago today, this was highlighted in an episode of Numberphile, precipitating (of course) a couple of new records:

Two days after the video, gamer Gelly Gelbertson found 10^10056+10^6692+10^5872+1 [p] (a 10057-digit term in OEIS A393530). Another two days and Vishwath Ganesan discovered 10^20000+518406362*10^9996+1 [p] (a 20001-digit emirp). As Vish's record was not initially noted beyond his PrimeGrid Discord chat, it created, unfortunately, a large number of claims of record that were (being fewer than 20001 digits and coming after February 20) not actually records. That included a 10069-digit (still not proven) random emirp made possible by AI.

Updates
March 19: Serge Batalov captured a near-repunit 10^22822-10^63-1 [p] emirp.
March 26: Justin Auger posted 10^39988+5417497422*10^19990+1 [p].
March 27: Serge Batalov posted 10^47253-22*10^21607-1 [p].

Email me if you spot any errors or have something to add.

1 comment:

  1. Well guys, n = 11111 was just a math exercise for me, but now the challenge is accepted!

    ReplyDelete