809905 has 8 divisors (see below), whose sum is σ = 994752. Its totient is φ = 632688.

The previous prime is 809903. The next prime is 809909. The reversal of 809905 is 509908.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 809905 - 2¹ = 809903 is a prime.

It is a super-2 number, since 2×809905² = 1311892218050, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (809903) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1669 + ... + 2098.

It is an arithmetic number, because the mean of its divisors is an integer number (124344).

2⁸⁰⁹⁹⁰⁵ is an apocalyptic number.

It is an amenable number.

809905 is a deficient number, since it is larger than the sum of its proper divisors (184847).

809905 is a wasteful number, since it uses less digits than its factorization.

809905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3815.

The product of its (nonzero) digits is 3240, while the sum is 31.

The square root of 809905 is about 899.9472206746. The cubic root of 809905 is about 93.2133307511.

The spelling of 809905 in words is "eight hundred nine thousand, nine hundred five".