840405 has 16 divisors (see below), whose sum is σ = 1356480. Its totient is φ = 444288.

The previous prime is 840353. The next prime is 840439. The reversal of 840405 is 504048.

It is not a de Polignac number, because 840405 - 2⁶ = 840341 is a prime.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 840405.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2529 + ... + 2841.

It is an arithmetic number, because the mean of its divisors is an integer number (84780).

2⁸⁴⁰⁴⁰⁵ is an apocalyptic number.

It is an amenable number.

840405 is a deficient number, since it is larger than the sum of its proper divisors (516075).

840405 is a wasteful number, since it uses less digits than its factorization.

840405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 500.

The product of its (nonzero) digits is 640, while the sum is 21.

The square root of 840405 is about 916.7360579796. The cubic root of 840405 is about 94.3690411863.

The spelling of 840405 in words is "eight hundred forty thousand, four hundred five".