644771400 has 384 divisors, whose sum is σ = 2520672000. Its totient is φ = 135475200.

The previous prime is 644771381. The next prime is 644771417. The reversal of 644771400 is 4177446.

644771400 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 2675280 + ... + 2675520.

It is an arithmetic number, because the mean of its divisors is an integer number (6564250).

Almost surely, 2^644771400 is an apocalyptic number.

644771400 is a gapful number since it is divisible by the number (60) 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 644771400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1260336000).

644771400 is an abundant number, since it is smaller than the sum of its proper divisors (1875900600).

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

644771400 is a wasteful number, since it uses less digits than its factorization.

644771400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 294 (or 271 counting only the distinct ones).

The product of its (nonzero) digits is 18816, while the sum is 33.

The square root of 644771400 is about 25392.3492414546. The cubic root of 644771400 is about 863.9101737033.

The spelling of 644771400 in words is "six hundred forty-four million, seven hundred seventy-one thousand, four hundred".