21031
domain: N
Properties
Primality
- Prime
- yes
Appears in sequences
- Primes of the form k^2+6.at n=14A056909
- Primes with 12 as smallest positive primitive root.at n=7A061325
- Primes for which the five closest primes are smaller.at n=9A075037
- 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=26A075595
- Numbers k such that k, sigma(k) and phi(k) have the same decimal digits (ignoring multiplicity).at n=29A082059
- Primes from merging of 5 successive digits in decimal expansion of the Champernowne Constant.at n=22A104948
- prime(k) for those k where floor((2*(prime(k+1)-prime(k))*PrimePi(k) mod (8*k))/k) = m with m = 8.at n=37A109562
- Primes p such that q-p = 28, where q is the next prime after p.at n=17A124595
- Prime sequence overlaying the central digits of prime numbers. If possible, the value is greater than the previous one. Zero if no such embedding is possible.at n=26A133781
- Primes congruent to 47 mod 61.at n=39A142845
- Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 0), (-1, 1, -1), (0, 0, 1), (0, 1, 0), (1, 0, -1)}.at n=9A149865
- Primes obtained from other primes by pre-concatenating with 2.at n=38A165243
- Primes p dividing every A167859(m) from m=(p-1)/2 to m=(p-1).at n=27A167860
- Counting integers normally (1, 2, 3, 4, 5...), write them as roman numerals (I, II, III, IV, V...), describe them (one 1, two 1s, three 1s, one 1 one 5, one 5...), and write them out as numbers (11, 21, 31, 1115, 15...).at n=22A180105
- Primes p whose smallest positive primitive root (mod p) is not squarefree.at n=7A205581
- Primes of the form 2*n^2 + 58*n + 27.at n=19A217498
- Prime(n), where n is such that (1+sum_{i=1..n} prime(i)^14) / n is an integer.at n=26A233043
- Number of magic labelings of the prism graph I X C_5 with magic sum n.at n=10A244497
- Primes such that A271229(n) = prime(n).at n=28A276649
- a(1) = 2; a(n + 1) = smallest prime > a(n) such that a(n + 1) - a(n) is the product of 7 primes.at n=35A285692