644140561752400 has 120 divisors (see below), whose sum is σ = 1562210562731904. Its totient is φ = 255223081344000.

The previous prime is 644140561752323. The next prime is 644140561752407. The reversal of 644140561752400 is 4257165041446.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644140561752407) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 12678675 + ... + 38066125.

Almost surely, 2^{644140561752400} is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644140561752400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (781105281365952).

644140561752400 is an abundant number, since it is smaller than the sum of its proper divisors (918070000979504).

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

644140561752400 is a wasteful number, since it uses less digits than its factorization.

644140561752400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25388069 (or 25388058 counting only the distinct ones).

The product of its (nonzero) digits is 3225600, while the sum is 49.

The spelling of 644140561752400 in words is "six hundred forty-four trillion, one hundred forty billion, five hundred sixty-one million, seven hundred fifty-two thousand, four hundred".