644532577920 has 2016 divisors, whose sum is σ = 2966565534660. Its totient is φ = 133354045440.

The previous prime is 644532577873. The next prime is 644532577937. The reversal of 644532577920 is 29775235446.

644532577920 is a `hidden beast` number, since 6 + 4 + 45 + 3 + 2 + 577 + 9 + 20 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 611061143616 + 33471434304 = 781704^2 + 182952^2 .

It is a tau number, because it is divible by the number of its divisors (2016).

It is a Harshad number since it is a multiple of its sum of digits (54).

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 251 ways as a sum of consecutive naturals, for example, 2766234124 + ... + 2766234356.

Almost surely, 2^644532577920 is an apocalyptic number.

644532577920 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 644532577920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1483282767330).

644532577920 is an abundant number, since it is smaller than the sum of its proper divisors (2322032956740).

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

644532577920 is a wasteful number, since it uses less digits than its factorization.

644532577920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 306 (or 261 counting only the distinct ones).

The product of its (nonzero) digits is 12700800, while the sum is 54.

The spelling of 644532577920 in words is "six hundred forty-four billion, five hundred thirty-two million, five hundred seventy-seven thousand, nine hundred twenty".