644864000 has 192 divisors, whose sum is σ = 1763143200. Its totient is φ = 233472000.

The previous prime is 644863979. The next prime is 644864021. The reversal of 644864000 is 468446.

It is an interprime number because it is at equal distance from previous prime (644863979) and next prime (644864021).

It is a Harshad number since it is a multiple of its sum of digits (32).

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 15 ways as a sum of consecutive naturals, for example, 2815886 + ... + 2816114.

Almost surely, 2^644864000 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644864000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (881571600).

644864000 is an abundant number, since it is smaller than the sum of its proper divisors (1118279200).

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

644864000 is a wasteful number, since it uses less digits than its factorization.

644864000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 277 (or 247 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 32.

The square root of 644864000 is about 25394.1725598611. The cubic root of 644864000 is about 863.9515290595.

It can be divided in two parts, 64486 and 4000, that added together give a palindrome (68486).

The spelling of 644864000 in words is "six hundred forty-four million, eight hundred sixty-four thousand".