864721440 has 384 divisors, whose sum is σ = 3413975040. Its totient is φ = 202521600.

The previous prime is 864721433. The next prime is 864721477. The reversal of 864721440 is 44127468.

864721440 is a `hidden beast` number, since 8 + 647 + 2 + 1 + 4 + 4 + 0 = 666.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 864721395 and 864721404.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1472827 + ... + 1473413.

It is an arithmetic number, because the mean of its divisors is an integer number (8890560).

Almost surely, 2^864721440 is an apocalyptic number.

864721440 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 864721440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1706987520).

864721440 is an abundant number, since it is smaller than the sum of its proper divisors (2549253600).

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

864721440 is a wasteful number, since it uses less digits than its factorization.

864721440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 653 (or 639 counting only the distinct ones).

The product of its (nonzero) digits is 43008, while the sum is 36.

The square root of 864721440 is about 29406.1462963102. The cubic root of 864721440 is about 952.7056534058.

The spelling of 864721440 in words is "eight hundred sixty-four million, seven hundred twenty-one thousand, four hundred forty".