644331400 has 48 divisors (see below), whose sum is σ = 1534628340. Its totient is φ = 251443200.

The previous prime is 644331383. The next prime is 644331403. The reversal of 644331400 is 4133446.

It is a happy number.

It can be written as a sum of positive squares in 6 ways, for example, as 192598884 + 451732516 = 13878^2 + 21254^2 .

It is a Harshad number since it is a multiple of its sum of digits (25).

It is not an unprimeable number, because it can be changed into a prime (644331403) 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, 31089 + ... + 47488.

Almost surely, 2^644331400 is an apocalyptic number.

It is an amenable number.

644331400 is an abundant number, since it is smaller than the sum of its proper divisors (890296940).

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

644331400 is a wasteful number, since it uses less digits than its factorization.

644331400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78634 (or 78625 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 25.

The square root of 644331400 is about 25383.6837358174. The cubic root of 644331400 is about 863.7136146461.

Adding to 644331400 its reverse (4133446), we get a palindrome (648464846).

The spelling of 644331400 in words is "six hundred forty-four million, three hundred thirty-one thousand, four hundred".