861865 has 4 divisors (see below), whose sum is σ = 1034244. Its totient is φ = 689488.

The previous prime is 861857. The next prime is 861871. The reversal of 861865 is 568168.

It is a happy number.

861865 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 535824 + 326041 = 732^2 + 571^2 .

It is a cyclic number.

It is not a de Polignac number, because 861865 - 2³ = 861857 is a prime.

It is a super-2 number, since 2×861865² = 1485622556450, 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 861865.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 86182 + ... + 86191.

It is an arithmetic number, because the mean of its divisors is an integer number (258561).

2⁸⁶¹⁸⁶⁵ is an apocalyptic number.

It is an amenable number.

861865 is a deficient number, since it is larger than the sum of its proper divisors (172379).

861865 is a wasteful number, since it uses less digits than its factorization.

861865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 172378.

The product of its digits is 11520, while the sum is 34.

The square root of 861865 is about 928.3668455950. The cubic root of 861865 is about 95.1655469920.

The spelling of 861865 in words is "eight hundred sixty-one thousand, eight hundred sixty-five".