840440 has 16 divisors (see below), whose sum is σ = 1891080. Its totient is φ = 336160.

The previous prime is 840439. The next prime is 840451. The reversal of 840440 is 44048.

It is a Harshad number since it is a multiple of its sum of digits (20).

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 840440.

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 3 ways as a sum of consecutive naturals, for example, 10466 + ... + 10545.

2⁸⁴⁰⁴⁴⁰ is an apocalyptic number.

It is an amenable number.

840440 is an abundant number, since it is smaller than the sum of its proper divisors (1050640).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

840440 is a wasteful number, since it uses less digits than its factorization.

840440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21022 (or 21018 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 20.

The square root of 840440 is about 916.7551472449. The cubic root of 840440 is about 94.3703512176.

Adding to 840440 its reverse (44048), we get a palindrome (884488).

The spelling of 840440 in words is "eight hundred forty thousand, four hundred forty".