840909 has 4 divisors (see below), whose sum is σ = 1121216. Its totient is φ = 560604.

The previous prime is 840907. The next prime is 840911. The reversal of 840909 is 909048.

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 an interprime number because it is at equal distance from previous prime (840907) and next prime (840911).

It is not a de Polignac number, because 840909 - 2¹ = 840907 is a prime.

It is a D-number.

It is a Duffinian number.

840909 is a modest number, since divided by 909 gives 84 as remainder.

840909 is a lucky number.

It is a plaindrome in base 12.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (840907) by changing a digit.

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, 140149 + ... + 140154.

It is an arithmetic number, because the mean of its divisors is an integer number (280304).

2⁸⁴⁰⁹⁰⁹ is an apocalyptic number.

It is an amenable number.

840909 is a deficient number, since it is larger than the sum of its proper divisors (280307).

840909 is a wasteful number, since it uses less digits than its factorization.

840909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 280306.

The product of its (nonzero) digits is 2592, while the sum is 30.

The square root of 840909 is about 917.0109050606. The cubic root of 840909 is about 94.3879021292.

The spelling of 840909 in words is "eight hundred forty thousand, nine hundred nine".