405809 has 4 divisors (see below), whose sum is σ = 407616. Its totient is φ = 404004.

The previous prime is 405799. The next prime is 405817. The reversal of 405809 is 908504.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 405809 - 2⁸ = 405553 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 405809.

It is not an unprimeable number, because it can be changed into a prime (405829) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 509 + ... + 1034.

It is an arithmetic number, because the mean of its divisors is an integer number (101904).

2⁴⁰⁵⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

405809 is a deficient number, since it is larger than the sum of its proper divisors (1807).

405809 is a wasteful number, since it uses less digits than its factorization.

405809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1806.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 405809 is about 637.0313964005. The cubic root of 405809 is about 74.0355928119.

It can be divided in two parts, 405 and 809, that multiplied together give a triangular number (327645 = T₈₀₉).

The spelling of 405809 in words is "four hundred five thousand, eight hundred nine".