866861 has 4 divisors (see below), whose sum is σ = 870492. Its totient is φ = 863232.

The previous prime is 866857. The next prime is 866869. The reversal of 866861 is 168668.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 855625 + 11236 = 925^2 + 106^2 .

It is a cyclic number.

It is not a de Polignac number, because 866861 - 2² = 866857 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (866869) 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, 1430 + ... + 1943.

It is an arithmetic number, because the mean of its divisors is an integer number (217623).

2⁸⁶⁶⁸⁶¹ is an apocalyptic number.

It is an amenable number.

866861 is a deficient number, since it is larger than the sum of its proper divisors (3631).

866861 is a wasteful number, since it uses less digits than its factorization.

866861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3630.

The product of its digits is 13824, while the sum is 35.

The square root of 866861 is about 931.0537041439. The cubic root of 866861 is about 95.3490758665.

The spelling of 866861 in words is "eight hundred sixty-six thousand, eight hundred sixty-one".