644144400 has 315 divisors, whose sum is σ = 2370691861. Its totient is φ = 168117120.

The previous prime is 644144377. The next prime is 644144401. The reversal of 644144400 is 4441446.

The square root of 644144400 is 25380.

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

644144400 is a `hidden beast` number, since 644 + 14 + 4 + 4 + 0 + 0 = 666.

It can be written as a sum of positive squares in only one way, i.e., 231891984 + 412252416 = 15228^2 + 20304^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644144401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 62 ways as a sum of consecutive naturals, for example, 13705177 + ... + 13705223.

Almost surely, 2^644144400 is an apocalyptic number.

644144400 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

644144400 is the 25380-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644144400

644144400 is an abundant number, since it is smaller than the sum of its proper divisors (1726547461).

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

644144400 is an equidigital number, since it uses as much as digits as its factorization.

644144400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 130 (or 57 counting only the distinct ones).

The product of its (nonzero) digits is 6144, while the sum is 27.

The cubic root of 644144400 is about 863.6300499496.

Adding to 644144400 its reverse (4441446), we get a palindrome (648585846).

The spelling of 644144400 in words is "six hundred forty-four million, one hundred forty-four thousand, four hundred".