400809 has 16 divisors (see below), whose sum is σ = 587520. Its totient is φ = 241920.

The previous prime is 400759. The next prime is 400823. The reversal of 400809 is 908004.

It is not a de Polignac number, because 400809 - 2⁷ = 400681 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (400849) 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, 1344 + ... + 1614.

It is an arithmetic number, because the mean of its divisors is an integer number (36720).

2⁴⁰⁰⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

400809 is a deficient number, since it is larger than the sum of its proper divisors (186711).

400809 is a wasteful number, since it uses less digits than its factorization.

400809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320.

The product of its (nonzero) digits is 288, while the sum is 21.

The square root of 400809 is about 633.0947796341. The cubic root of 400809 is about 73.7302695472.

The spelling of 400809 in words is "four hundred thousand, eight hundred nine".