865981 has 4 divisors (see below), whose sum is σ = 868000. Its totient is φ = 863964.

The previous prime is 865979. The next prime is 865993. The reversal of 865981 is 189568.

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 865981 - 2¹ = 865979 is a prime.

It is a super-2 number, since 2×865981² = 1499846184722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 865981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (865481) 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, 81 + ... + 1318.

It is an arithmetic number, because the mean of its divisors is an integer number (217000).

2⁸⁶⁵⁹⁸¹ is an apocalyptic number.

It is an amenable number.

865981 is a deficient number, since it is larger than the sum of its proper divisors (2019).

865981 is a wasteful number, since it uses less digits than its factorization.

865981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2018.

The product of its digits is 17280, while the sum is 37.

The square root of 865981 is about 930.5810013105. The cubic root of 865981 is about 95.3168001822.

The spelling of 865981 in words is "eight hundred sixty-five thousand, nine hundred eighty-one".