644334543325440 has 1728 divisors, whose sum is σ = 2603590960239360. Its totient is φ = 145389634191360.

The previous prime is 644334543325357. The next prime is 644334543325483. The reversal of 644334543325440 is 44523345433446.

644334543325440 is a `hidden beast` number, since 6 + 4 + 4 + 3 + 3 + 4 + 543 + 3 + 2 + 54 + 40 = 666.

It is an unprimeable number.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 156050989296 + ... + 156050993424.

It is an arithmetic number, because the mean of its divisors is an integer number (1506707731620).

Almost surely, 2^{644334543325440} is an apocalyptic number.

644334543325440 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 644334543325440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1301795480119680).

644334543325440 is an abundant number, since it is smaller than the sum of its proper divisors (1959256416913920).

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

644334543325440 is a wasteful number, since it uses less digits than its factorization.

644334543325440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4968 (or 4951 counting only the distinct ones).

The product of its (nonzero) digits is 99532800, while the sum is 54.

Adding to 644334543325440 its reverse (44523345433446), we get a palindrome (688857888758886).

The spelling of 644334543325440 in words is "six hundred forty-four trillion, three hundred thirty-four billion, five hundred forty-three million, three hundred twenty-five thousand, four hundred forty".