865665820 has 12 divisors (see below), whose sum is σ = 1817898264. Its totient is φ = 346266320.

The previous prime is 865665817. The next prime is 865665833. The reversal of 865665820 is 28566568.

It is a congruent number.

It is an unprimeable number.

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, 21641626 + ... + 21641665.

It is an arithmetic number, because the mean of its divisors is an integer number (151491522).

Almost surely, 2^865665820 is an apocalyptic number.

It is an amenable number.

865665820 is an abundant number, since it is smaller than the sum of its proper divisors (952232444).

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

865665820 is a wasteful number, since it uses less digits than its factorization.

865665820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43283300 (or 43283298 counting only the distinct ones).

The product of its (nonzero) digits is 691200, while the sum is 46.

The square root of 865665820 is about 29422.1994419180. The cubic root of 865665820 is about 953.0523503454.

The spelling of 865665820 in words is "eight hundred sixty-five million, six hundred sixty-five thousand, eight hundred twenty".