644503540 has 24 divisors (see below), whose sum is σ = 1400129640. Its totient is φ = 248911488.

The previous prime is 644503513. The next prime is 644503543. The reversal of 644503540 is 45305446.

It can be written as a sum of positive squares in 4 ways, for example, as 54110736 + 590392804 = 7356^2 + 24298^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644503543) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 555027 + ... + 556186.

It is an arithmetic number, because the mean of its divisors is an integer number (58338735).

Almost surely, 2^644503540 is an apocalyptic number.

It is an amenable number.

644503540 is an abundant number, since it is smaller than the sum of its proper divisors (755626100).

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

644503540 is a wasteful number, since it uses less digits than its factorization.

644503540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1111251 (or 1111249 counting only the distinct ones).

The product of its (nonzero) digits is 28800, while the sum is 31.

The square root of 644503540 is about 25387.0742701872. The cubic root of 644503540 is about 863.7905245629.

Adding to 644503540 its reverse (45305446), we get a palindrome (689808986).

The spelling of 644503540 in words is "six hundred forty-four million, five hundred three thousand, five hundred forty".