309809 has 6 divisors (see below), whose sum is σ = 318690. Its totient is φ = 301136.

The previous prime is 309797. The next prime is 309811. The reversal of 309809 is 908903.

It can be written as a sum of positive squares in only one way, i.e., 222784 + 87025 = 472^2 + 295^2 .

It is a de Polignac number, because none of the positive numbers 2^k-309809 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 309809.

It is not an unprimeable number, because it can be changed into a prime (309899) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3437 + ... + 3525.

It is an arithmetic number, because the mean of its divisors is an integer number (53115).

2³⁰⁹⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

309809 is a deficient number, since it is larger than the sum of its proper divisors (8881).

309809 is an frugal number, since it uses more digits than its factorization.

309809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 207 (or 148 counting only the distinct ones).

The product of its (nonzero) digits is 1944, while the sum is 29.

The square root of 309809 is about 556.6048867913. The cubic root of 309809 is about 67.6650920010.

The spelling of 309809 in words is "three hundred nine thousand, eight hundred nine".