866191 has 4 divisors (see below), whose sum is σ = 911800. Its totient is φ = 820584.

The previous prime is 866183. The next prime is 866197. The reversal of 866191 is 191668.

It is a happy number.

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 866191 - 2³ = 866183 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (866197) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 22776 + ... + 22813.

It is an arithmetic number, because the mean of its divisors is an integer number (227950).

2⁸⁶⁶¹⁹¹ is an apocalyptic number.

866191 is a deficient number, since it is larger than the sum of its proper divisors (45609).

866191 is a wasteful number, since it uses less digits than its factorization.

866191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45608.

The product of its digits is 2592, while the sum is 31.

The square root of 866191 is about 930.6938272063. The cubic root of 866191 is about 95.3245043198.

The spelling of 866191 in words is "eight hundred sixty-six thousand, one hundred ninety-one".