809991866 has 16 divisors (see below), whose sum is σ = 1257719400. Its totient is φ = 390770688.

The previous prime is 809991829. The next prime is 809991881. The reversal of 809991866 is 668199908.

It can be written as a sum of positive squares in 4 ways, for example, as 570206641 + 239785225 = 23879^2 + 15485^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 105866 + ... + 113258.

Almost surely, 2^809991866 is an apocalyptic number.

809991866 is a deficient number, since it is larger than the sum of its proper divisors (447727534).

809991866 is a wasteful number, since it uses less digits than its factorization.

809991866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9313.

The product of its (nonzero) digits is 1679616, while the sum is 56.

The square root of 809991866 is about 28460.3560413428. The cubic root of 809991866 is about 932.1666315005.

The spelling of 809991866 in words is "eight hundred nine million, nine hundred ninety-one thousand, eight hundred sixty-six".