The Top Twenty--a Prime Page Collection

Near-repdigit

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The Prime Pages keeps a list of the 5000 largest known primes, plus a few each of certain selected archivable forms and classes. These forms are defined in this collection's home page. This page is about one of those forms. Comments and suggestions requested.

(up) Definitions and Notes

A repunit is a number of the form 11111...111 (repeated units). In base two (binary), these are the Mersenne primes. In base ten, just a few are known. If we repeat any other digit, then we get a composite (e.g., 777777 is divisible by 7).

To get a more general form, two things have been tried:

  1. Let one of the digits differ from one--these are the near repunit primes.
  2. Let all but one of the digits be the same, these are the near repdigit primes (and include the near repunit primes).

(up) Record Primes of this Type

rankprime digitswhowhencomment
12 · 101059002 - 1 1059003 L3432 Sep 2013 Near - repdigit
29 · 101009567 - 1 1009568 L3735 Sep 2016 Near - repdigit
396 · 10846519 - 1 846521 L2425 Sep 2011 Near - repdigit
492 · 10833852 - 1 833854 L4789 Apr 2018 Near - repdigit
58 · 10608989 - 1 608990 p297 May 2011 Near - repdigit
692 · 10544905 - 1 544907 L3735 May 2015 Near - repdigit
75 · 10511056 - 1 511057 p297 Mar 2011 Near - repdigit
895 · 10466002 - 1 466004 L3735 May 2014 Near - repdigit
95 · 10464843 - 1 464844 p297 Feb 2011 Near - repdigit
105 · 10445773 - 1 445774 p297 Jan 2011 Near - repdigit
116 · 10414508 - 1 414509 p297 Jan 2011 Near - repdigit
1299998 · 10389150 - 1 389155 L3432 Sep 2016 Near - repdigit
1310388080 - 10112433 - 1 388080 CH8 Nov 2014 Near - repdigit
1410388080 - 10180868 - 1 388080 p377 Nov 2014 Near - repdigit
1510388080 - 10332944 - 1 388080 p377 Dec 2014 Near - repdigit
1610388080 - 10342029 - 1 388080 p377 Dec 2014 Near - repdigit
1799999995 · 10386956 - 1 386964 L3432 Sep 2016 Near - repdigit
189 · 10383643 - 1 383644 p297 Jan 2011 Near - repdigit
199999998 · 10369705 - 1 369712 L1958 Jan 2014 Near - repdigit
209 · 10364521 - 1 364522 p297 Dec 2010 Near - repdigit

(up) References

Caldwell89
C. Caldwell, "The near repdigit primes 333 ... 331," J. Recreational Math., 21:4 (1989) 299--304.
Caldwell90
C. Caldwell, "The near repdigit primes AnB, ABn, and UBASIC," J. Recreational Math., 22:2 (1990) 100--109.
CD95
C. Caldwell and H. Dubner, "The near repunit primes 1n-k-1011k," J. Recreational Math., 27 (1995) 35--41.
CD97
C. Caldwell and H. Dubner, "The near repdigit primes An-k-1B1Ak, especially 9n-k-1819k," J. Recreational Math., 28:1 (1996-97) 1--9.
Heleen98
Heleen, J. P., "More near-repunit primes 1n-k-1D11k, D=2,3, ..., 9," J. Recreational Math., 29:3 (1998) 190--195.
Williams78b
H. C. Williams, "Some primes with interesting digit patterns," Math. Comp., 32 (1978) 1306--1310.  Corrigendum in 39 (1982), 759.  MR 58:484
Chris K. Caldwell © 1996-2018 (all rights reserved)