644811904 has 192 divisors, whose sum is σ = 1562803200. Its totient is φ = 263577600.

The previous prime is 644811901. The next prime is 644811917. The reversal of 644811904 is 409118446.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644811901) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 8162137 + ... + 8162215.

It is an arithmetic number, because the mean of its divisors is an integer number (8139600).

Almost surely, 2^644811904 is an apocalyptic number.

644811904 is a gapful number since it is divisible by the number (64) 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 644811904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (781401600).

644811904 is an abundant number, since it is smaller than the sum of its proper divisors (917991296).

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

644811904 is a wasteful number, since it uses less digits than its factorization.

644811904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 163 (or 140 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 37.

The square root of 644811904 is about 25393.1467919988. The cubic root of 644811904 is about 863.9282633627.

The spelling of 644811904 in words is "six hundred forty-four million, eight hundred eleven thousand, nine hundred four".