856409 has 4 divisors (see below), whose sum is σ = 906804. Its totient is φ = 806016.

The previous prime is 856393. The next prime is 856411. The reversal of 856409 is 904658.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 904658 = 2 ⋅452329.

It can be written as a sum of positive squares in 2 ways, for example, as 644809 + 211600 = 803^2 + 460^2 .

It is a cyclic number.

It is not a de Polignac number, because 856409 - 2⁴ = 856393 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 856409.

It is not an unprimeable number, because it can be changed into a prime (856459) 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, 25172 + ... + 25205.

It is an arithmetic number, because the mean of its divisors is an integer number (226701).

2⁸⁵⁶⁴⁰⁹ is an apocalyptic number.

It is an amenable number.

856409 is a deficient number, since it is larger than the sum of its proper divisors (50395).

856409 is a wasteful number, since it uses less digits than its factorization.

856409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50394.

The product of its (nonzero) digits is 8640, while the sum is 32.

The square root of 856409 is about 925.4236867511. The cubic root of 856409 is about 94.9643079216.

The spelling of 856409 in words is "eight hundred fifty-six thousand, four hundred nine".