644424400 has 60 divisors (see below), whose sum is σ = 1570104864. Its totient is φ = 254128000.

The previous prime is 644424397. The next prime is 644424401. The reversal of 644424400 is 4424446.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644424401) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 17055 + ... + 39745.

Almost surely, 2^644424400 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 644424400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (785052432).

644424400 is an abundant number, since it is smaller than the sum of its proper divisors (925680464).

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

644424400 is a wasteful number, since it uses less digits than its factorization.

644424400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22780 (or 22769 counting only the distinct ones).

The product of its (nonzero) digits is 12288, while the sum is 28.

The square root of 644424400 is about 25385.5155551350. The cubic root of 644424400 is about 863.7551675395.

Adding to 644424400 its reverse (4424446), we get a palindrome (648848846).

The spelling of 644424400 in words is "six hundred forty-four million, four hundred twenty-four thousand, four hundred".