840561 has 4 divisors (see below), whose sum is σ = 1120752. Its totient is φ = 560372.

The previous prime is 840557. The next prime is 840571. The reversal of 840561 is 165048.

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 840561 - 2² = 840557 is a prime.

It is a D-number.

840561 is a lucky number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 840561.

It is not an unprimeable number, because it can be changed into a prime (840571) 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, 140091 + ... + 140096.

It is an arithmetic number, because the mean of its divisors is an integer number (280188).

2⁸⁴⁰⁵⁶¹ is an apocalyptic number.

It is an amenable number.

840561 is a deficient number, since it is larger than the sum of its proper divisors (280191).

840561 is a wasteful number, since it uses less digits than its factorization.

840561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 280190.

The product of its (nonzero) digits is 960, while the sum is 24.

The square root of 840561 is about 916.8211384998. The cubic root of 840561 is about 94.3748799028.

The spelling of 840561 in words is "eight hundred forty thousand, five hundred sixty-one".