644409216 has 384 divisors, whose sum is σ = 2213971200. Its totient is φ = 183997440.

The previous prime is 644409197. The next prime is 644409287. The reversal of 644409216 is 612904446.

644409216 is a `hidden beast` number, since 644 + 4 + 0 + 9 + 2 + 1 + 6 = 666.

It is a tau number, because it is divible by the number of its divisors (384).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 9618015 + ... + 9618081.

It is an arithmetic number, because the mean of its divisors is an integer number (5765550).

Almost surely, 2^644409216 is an apocalyptic number.

644409216 is a gapful number since it is divisible by the number (66) 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 644409216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1106985600).

644409216 is an abundant number, since it is smaller than the sum of its proper divisors (1569561984).

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

644409216 is a wasteful number, since it uses less digits than its factorization.

644409216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 135 (or 106 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 36.

The square root of 644409216 is about 25385.2164851907. The cubic root of 644409216 is about 863.7483835208.

The spelling of 644409216 in words is "six hundred forty-four million, four hundred nine thousand, two hundred sixteen".