865840 has 40 divisors (see below), whose sum is σ = 2053440. Its totient is φ = 339456.

The previous prime is 865829. The next prime is 865847. The reversal of 865840 is 48568.

It is a tau number, because it is divible by the number of its divisors (40).

It is not an unprimeable number, because it can be changed into a prime (865847) by changing a digit.

865840 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6252 + ... + 6388.

It is an arithmetic number, because the mean of its divisors is an integer number (51336).

2⁸⁶⁵⁸⁴⁰ is an apocalyptic number.

865840 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 865840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1026720).

865840 is an abundant number, since it is smaller than the sum of its proper divisors (1187600).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

865840 is a wasteful number, since it uses less digits than its factorization.

865840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 229 (or 223 counting only the distinct ones).

The product of its (nonzero) digits is 7680, while the sum is 31.

The square root of 865840 is about 930.5052391040. The cubic root of 865840 is about 95.3116267052.

The spelling of 865840 in words is "eight hundred sixty-five thousand, eight hundred forty".