644066000 has 80 divisors (see below), whose sum is σ = 1564774848. Its totient is φ = 256400000.

The previous prime is 644065969. The next prime is 644066041. The reversal of 644066000 is 660446.

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 501359 + ... + 502641.

Almost surely, 2^644066000 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 644066000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (782387424).

644066000 is an abundant number, since it is smaller than the sum of its proper divisors (920708848).

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

644066000 is a wasteful number, since it uses less digits than its factorization.

644066000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1557 (or 1541 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 26.

The square root of 644066000 is about 25378.4554297538. The cubic root of 644066000 is about 863.5950105273.

The spelling of 644066000 in words is "six hundred forty-four million, sixty-six thousand".