### Properties of the number 839:

839 is a cyclic number.839 is the 146

^{th}prime.

839 has 9 antidivisors and 838 totatives.

839 has an oblong digit sum 20 in base 10.

Reversing the decimal digits of 839 results in a sphenic number.

839 = 420

^{2}- 419

^{2}is the difference of 2 nonnegative squares in 1 way.

839 is the sum of 2 positive triangular numbers.

839 is the difference of 2 positive pentagonal numbers in 1 way.

839 is not the sum of 3 positive squares.

839

^{2}is the sum of 3 positive squares.

839 is a proper divisor of 2

^{419}- 1.

839 is an emirp in (at least) the following bases: 2, 7, 11, 12, 21, 25, 26, 27, 29, 31, 33, 35, 36, 37, 42, 44, 49, 53, 57, 61, 64, 65, 67, 71, 74, 75, 76, 77, 79, 83, 85, 89, and 92.

839 is palindromic in (at least) the following bases: 4, -10, -19, and -27.

839 in base 28 = 11r and consists of only the digits '1' and 'r'.

### The number 839 belongs to the following On-Line Encyclopedia of Integer Sequences (OEIS) sequences (among others):

Sequence numbers and descriptions below are taken from OEIS.A000928: Irregular primes: p is regular if and only if the numerators of the Bernoulli numbers B_2, B_4, ..., B_{p-3} (A000367) are not divisible by p.

A005385: Safe primes p: (p-1)/2 is also prime.

A007522: Primes of the form 8n+7, that is, primes congruent to -1 mod 8.

A008865: a(n) = n^2 - 2.

A014616: a(n) = solution to the postage stamp problem with 2 denominations and n stamps.

A028871: Primes of the form n^2 - 2.

A068231: Primes congruent to 11 mod 12.

A107132: Primes of the form 2x^2 + 13y^2.

A141123: Primes of the form -x^2+2*x*y+2*y^2 (as well as of the form 3*x^2+6*x*y+2*y^2).

A235229: Numbers whose sum of digits is 20.

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