99999199999
domain: N
Appears in sequences
- Largest palindromic prime with 2n-1 digits.at n=5A028990
- Smallest prime beginning and ending in at least n 9's.at n=4A068163
- Palindromic wing primes (a.k.a. near-repdigit palindromic primes) of the general form r*(10^d - 1)/9 + (m-r)*10^floor(d/2) where d is the number of digits (an odd number > 1), r is the repeated digit, and m (different from r) is the middle digit.at n=32A077798
- Smallest palindromic prime containing exactly n 9's.at n=9A083980
- Palindromic primes in which a single digit is sandwiched between nonempty strings of 9's.at n=2A088284
- Smallest prime whose product of digits is 3^n.at n=20A088653
- Primes composed of digit {1,9} and with digit sum 9*k+1.at n=16A164890
- Smallest prime numbers p of length n having a decimal expansion x(1)x(2)... x(n) such that there exists an index j where x(j) = 1 and x(i) = 9 for i<>j, or 0 if no such prime exists.at n=9A241021
- Palindromic wing primes that are also Lychrel candidates.at n=3A320516
- Record gaps between palindromic primes (lower end): primes A002385(k) where A002385(k+1) - A002385(k) exceeds A002385(j+1) - A002385(j) for all j < k.at n=18A327428
- a(n) = 10^(2*n+1) - 1 - 8*10^n.at n=5A332191