865640880 has 240 divisors, whose sum is σ = 3267665856. Its totient is φ = 203765760.

The previous prime is 865640873. The next prime is 865640899. The reversal of 865640880 is 88046568.

865640880 is a `hidden beast` number, since 8 + 6 + 564 + 0 + 8 + 80 = 666.

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (45).

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 47 ways as a sum of consecutive naturals, for example, 213270 + ... + 217290.

Almost surely, 2^865640880 is an apocalyptic number.

865640880 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 865640880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1633832928).

865640880 is an abundant number, since it is smaller than the sum of its proper divisors (2402024976).

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

865640880 is a wasteful number, since it uses less digits than its factorization.

865640880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4076 (or 4067 counting only the distinct ones).

The product of its (nonzero) digits is 368640, while the sum is 45.

The square root of 865640880 is about 29421.7756092320. The cubic root of 865640880 is about 953.0431977166.

The spelling of 865640880 in words is "eight hundred sixty-five million, six hundred forty thousand, eight hundred eighty".