644989318144 has 66 divisors (see below), whose sum is σ = 1321566834662. Its totient is φ = 314628096000.

The previous prime is 644989318117. The next prime is 644989318177. The reversal of 644989318144 is 441813989446.

It can be written as a sum of positive squares in 3 ways, for example, as 12188160000 + 632801158144 = 110400^2 + 795488^2 .

It is a super-2 number, since 2×644989318144² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1533994 + ... + 1908694.

Almost surely, 2^644989318144 is an apocalyptic number.

644989318144 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 644989318144, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (660783417331).

644989318144 is an abundant number, since it is smaller than the sum of its proper divisors (676577516518).

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

644989318144 is an equidigital number, since it uses as much as digits as its factorization.

644989318144 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 374803 (or 374744 counting only the distinct ones).

The product of its digits is 23887872, while the sum is 61.

The spelling of 644989318144 in words is "six hundred forty-four billion, nine hundred eighty-nine million, three hundred eighteen thousand, one hundred forty-four".