644407000 has 64 divisors (see below), whose sum is σ = 1512613440. Its totient is φ = 256960000.

The previous prime is 644406991. The next prime is 644407003. The reversal of 644407000 is 704446.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644407003) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 400197 + ... + 401803.

It is an arithmetic number, because the mean of its divisors is an integer number (23634585).

Almost surely, 2^644407000 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 644407000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (756306720).

644407000 is an abundant number, since it is smaller than the sum of its proper divisors (868206440).

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

644407000 is a wasteful number, since it uses less digits than its factorization.

644407000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2029 (or 2015 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 25.

The square root of 644407000 is about 25385.1728377019. The cubic root of 644407000 is about 863.7473934312.

The spelling of 644407000 in words is "six hundred forty-four million, four hundred seven thousand".