809999989 has 2 divisors, whose sum is σ = 809999990. Its totient is φ = 809999988.

The previous prime is 809999959. The next prime is 809999999. The reversal of 809999989 is 989999908.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 597802500 + 212197489 = 24450^2 + 14567^2 .

It is a cyclic number.

It is not a de Polignac number, because 809999989 - 2²³ = 801611381 is a prime.

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, 404999994 + 404999995.

It is an arithmetic number, because the mean of its divisors is an integer number (404999995).

Almost surely, 2^809999989 is an apocalyptic number.

It is an amenable number.

809999989 is a deficient number, since it is larger than the sum of its proper divisors (1).

809999989 is an equidigital number, since it uses as much as digits as its factorization.

809999989 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 34012224, while the sum is 70.

The square root of 809999989 is about 28460.4987482651. The cubic root of 809999989 is about 932.1697475665.

The spelling of 809999989 in words is "eight hundred nine million, nine hundred ninety-nine thousand, nine hundred eighty-nine".