644540959104 has 128 divisors (see below), whose sum is σ = 1961807942400. Its totient is φ = 183668373504.

The previous prime is 644540959081. The next prime is 644540959141. The reversal of 644540959104 is 401959045446.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (128).

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 15 ways as a sum of consecutive naturals, for example, 702414 + ... + 1335090.

It is an arithmetic number, because the mean of its divisors is an integer number (15326624550).

Almost surely, 2^644540959104 is an apocalyptic number.

644540959104 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 644540959104, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (980903971200).

644540959104 is an abundant number, since it is smaller than the sum of its proper divisors (1317266983296).

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

644540959104 is a wasteful number, since it uses less digits than its factorization.

644540959104 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 633080 (or 633068 counting only the distinct ones).

The product of its (nonzero) digits is 3110400, while the sum is 51.

The spelling of 644540959104 in words is "six hundred forty-four billion, five hundred forty million, nine hundred fifty-nine thousand, one hundred four".