866891 has 4 divisors (see below), whose sum is σ = 872784. Its totient is φ = 861000.

The previous prime is 866869. The next prime is 866909. The reversal of 866891 is 198668.

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

It is a cyclic number.

It is not a de Polignac number, because 866891 - 2¹⁰ = 865867 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (866851) 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, 2720 + ... + 3021.

It is an arithmetic number, because the mean of its divisors is an integer number (218196).

2⁸⁶⁶⁸⁹¹ is an apocalyptic number.

866891 is a deficient number, since it is larger than the sum of its proper divisors (5893).

866891 is a wasteful number, since it uses less digits than its factorization.

866891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5892.

The product of its digits is 20736, while the sum is 38.

The square root of 866891 is about 931.0698147830. The cubic root of 866891 is about 95.3501757888.

The spelling of 866891 in words is "eight hundred sixty-six thousand, eight hundred ninety-one".