644841120400 has 45 divisors (see below), whose sum is σ = 1549269377833. Its totient is φ = 257930024000.

The previous prime is 644841120349. The next prime is 644841120409. The reversal of 644841120400 is 4021148446.

The square root of 644841120400 is 803020.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 232142803344 + 412698317056 = 481812^2 + 642416^2 .

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644841120409) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 16040325 + ... + 16080475.

Almost surely, 2^644841120400 is an apocalyptic number.

644841120400 is the 803020-th square number.

It is an amenable number.

644841120400 is an abundant number, since it is smaller than the sum of its proper divisors (904428257433).

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

644841120400 is an frugal number, since it uses more digits than its factorization.

644841120400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80320 (or 40158 counting only the distinct ones).

The product of its (nonzero) digits is 24576, while the sum is 34.

Adding to 644841120400 its reverse (4021148446), we get a palindrome (648862268846).

The spelling of 644841120400 in words is "six hundred forty-four billion, eight hundred forty-one million, one hundred twenty thousand, four hundred".