644440000 has 70 divisors (see below), whose sum is σ = 1598100944. Its totient is φ = 257760000.

The previous prime is 644439979. The next prime is 644440003. The reversal of 644440000 is 44446.

It is a happy number.

644440000 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644440003) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 31945 + ... + 48055.

Almost surely, 2^644440000 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 644440000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (799050472).

644440000 is an abundant number, since it is smaller than the sum of its proper divisors (953660944).

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

644440000 is an equidigital number, since it uses as much as digits as its factorization.

644440000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16143 (or 16118 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 22.

The square root of 644440000 is about 25385.8228151069. The cubic root of 644440000 is about 863.7621373107.

Adding to 644440000 its reverse (44446), we get a palindrome (644484446).

The spelling of 644440000 in words is "six hundred forty-four million, four hundred forty thousand".