866391991 has 8 divisors (see below), whose sum is σ = 906024960. Its totient is φ = 826922712.

The previous prime is 866391989. The next prime is 866391997. The reversal of 866391991 is 199193668.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 866391991 - 2¹ = 866391989 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 (866391997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 30031 + ... + 51328.

It is an arithmetic number, because the mean of its divisors is an integer number (113253120).

Almost surely, 2^866391991 is an apocalyptic number.

866391991 is a deficient number, since it is larger than the sum of its proper divisors (39632969).

866391991 is a wasteful number, since it uses less digits than its factorization.

866391991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81845.

The product of its digits is 629856, while the sum is 52.

The square root of 866391991 is about 29434.5373838285. The cubic root of 866391991 is about 953.3187678373.

The spelling of 866391991 in words is "eight hundred sixty-six million, three hundred ninety-one thousand, nine hundred ninety-one".