809999999 has 2 divisors, whose sum is σ = 810000000. Its totient is φ = 809999998.

The previous prime is 809999989. The next prime is 810000011. The reversal of 809999999 is 999999908.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-809999999 is a prime.

809999999 is a modest number, since divided by 99999 gives 8099 as remainder.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (809999929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 404999999 + 405000000.

It is an arithmetic number, because the mean of its divisors is an integer number (405000000).

Almost surely, 2^809999999 is an apocalyptic number.

809999999 is a deficient number, since it is larger than the sum of its proper divisors (1).

809999999 is an equidigital number, since it uses as much as digits as its factorization.

809999999 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 38263752, while the sum is 71.

The square root of 809999999 is about 28460.4989239472. The cubic root of 809999999 is about 932.1697514025.

The spelling of 809999999 in words is "eight hundred nine million, nine hundred ninety-nine thousand, nine hundred ninety-nine".