809999 has 16 divisors (see below), whose sum is σ = 933120. Its totient is φ = 698880.

The previous prime is 809993. The next prime is 810013. The reversal of 809999 is 999908.

809999 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Cunningham number, because it is equal to 30⁴-1.

It is a cyclic number.

It is not a de Polignac number, because 809999 - 2⁴ = 809983 is a prime.

It is a Duffinian number.

809999 is a modest number, since divided by 999 gives 809 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (809993) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15257 + ... + 15309.

It is an arithmetic number, because the mean of its divisors is an integer number (58320).

2⁸⁰⁹⁹⁹⁹ is an apocalyptic number.

809999 is a deficient number, since it is larger than the sum of its proper divisors (123121).

809999 is a wasteful number, since it uses less digits than its factorization.

809999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 130.

The product of its (nonzero) digits is 52488, while the sum is 44.

The square root of 809999 is about 899.9994444443. Note that the first 3 decimals coincide. The cubic root of 809999 is about 93.2169368177.

The spelling of 809999 in words is "eight hundred nine thousand, nine hundred ninety-nine".