864640 has 64 divisors (see below), whose sum is σ = 2374560. Its totient is φ = 294912.

The previous prime is 864631. The next prime is 864641. The reversal of 864640 is 46468.

It is a tau number, because it is divible by the number of its divisors (64).

It is a Harshad number since it is a multiple of its sum of digits (28).

It is an Ulam number.

It is a junction number, because it is equal to n+sod(n) for n = 864599 and 864608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (864641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4384 + ... + 4576.

2⁸⁶⁴⁶⁴⁰ is an apocalyptic number.

864640 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 864640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1187280).

864640 is an abundant number, since it is smaller than the sum of its proper divisors (1509920).

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

864640 is a wasteful number, since it uses less digits than its factorization.

864640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 219 (or 207 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 28.

The square root of 864640 is about 929.8602045469. The cubic root of 864640 is about 95.2675743664.

The spelling of 864640 in words is "eight hundred sixty-four thousand, six hundred forty".