21011

Properties

Appears in sequences

• Prime quadruples: numbers k such that k, k+2, k+6, k+8 are all prime.at n=19A007530
• Initial members p of prime 5-tuples (p, p+2, p+6, p+8, p+12).at n=6A022006
• n written in fractional base 3/2.at n=16A024629
• Primes p such that p+1 is palindromic.at n=29A028981
• Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 74 ones.at n=27A031842
• Initial terms of '4-block' primes as described in A032591.at n=32A032592
• Primes having only {0, 1, 2} as digits.at n=19A036953
• Lexicographically earliest strictly increasing base 3 autovarious sequence: a(n) = number of distinct a(k) mod 3^n (written in base 3).at n=27A037091
• Primes at which difference pattern X2424Y (X and Y >= 6) occurs in A001223.at n=1A052167
• Sum of composite numbers between prime p and nextprime(p) is palindromic.at n=21A054266
• Numbers k such that 2^k - 9 is prime.at n=23A059610
• Primes whose sum of digits is 5.at n=24A062341
• n*10^5-1, n*10^5-3, n*10^5-7 and n*10^5-9 are all prime.at n=6A064979
• Primes with arithmetic mean of digits = 1 (sum of digits = number of digits).at n=14A069710
• Duplicate of A069710.at n=14A073903
• Smallest prime that is obtained by placing digits on both sides of the n-th prime. Or smallest prime that encompasses the n-th prime.at n=25A075595
• Numbers k such that k, sigma(k) and phi(k) have the same decimal digits (ignoring multiplicity).at n=28A082059
• Prime numbers such that first reversing digits and after squaring equals the result of first-squaring and after-reversing. Primes in A085305.at n=33A085306
• Primes p such that three (the maximum number) primes occur between p and p+12.at n=14A086140
• Primes whose decimal representation also represents a prime in base 3.at n=7A089981