865820 has 12 divisors (see below), whose sum is σ = 1818264. Its totient is φ = 346320.

The previous prime is 865819. The next prime is 865829. The reversal of 865820 is 28568.

865820 = T₁₃₉ + T₁₄₀ + ... + T₁₉₈.

It is a happy number.

865820 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (865829) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21626 + ... + 21665.

It is an arithmetic number, because the mean of its divisors is an integer number (151522).

2⁸⁶⁵⁸²⁰ is an apocalyptic number.

It is an amenable number.

865820 is an abundant number, since it is smaller than the sum of its proper divisors (952444).

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

865820 is a wasteful number, since it uses less digits than its factorization.

865820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43300 (or 43298 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 29.

The square root of 865820 is about 930.4944921922. The cubic root of 865820 is about 95.3108928332.

The spelling of 865820 in words is "eight hundred sixty-five thousand, eight hundred twenty".