809856919 has 2 divisors, whose sum is σ = 809856920. Its totient is φ = 809856918.

The previous prime is 809856881. The next prime is 809857001. The reversal of 809856919 is 919658908.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 809856919 - 2²¹ = 807759767 is a prime.

It is a super-2 number, since 2×809856919² = 1311736458504345122, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 809856919.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (809856119) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 404928459 + 404928460.

It is an arithmetic number, because the mean of its divisors is an integer number (404928460).

Almost surely, 2^809856919 is an apocalyptic number.

809856919 is a deficient number, since it is larger than the sum of its proper divisors (1).

809856919 is an equidigital number, since it uses as much as digits as its factorization.

809856919 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1399680, while the sum is 55.

The square root of 809856919 is about 28457.9851535558. The cubic root of 809856919 is about 932.1148614017.

The spelling of 809856919 in words is "eight hundred nine million, eight hundred fifty-six thousand, nine hundred nineteen".