644537408 has 14 divisors (see below), whose sum is σ = 1279004046. Its totient is φ = 322268672.

The previous prime is 644537359. The next prime is 644537477. The reversal of 644537408 is 804735446.

It can be written as a sum of positive squares in only one way, i.e., 345662464 + 298874944 = 18592^2 + 17288^2 .

It is a super-2 number, since 2×644537408² = 830856940622716928, which contains 22 as substring.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 5035385 + ... + 5035512.

Almost surely, 2^644537408 is an apocalyptic number.

It is an amenable number.

644537408 is a deficient number, since it is larger than the sum of its proper divisors (634466638).

644537408 is a wasteful number, since it uses less digits than its factorization.

644537408 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10070909 (or 10070899 counting only the distinct ones).

The product of its (nonzero) digits is 322560, while the sum is 41.

The square root of 644537408 is about 25387.7412937819. The cubic root of 644537408 is about 863.8056547333.

The spelling of 644537408 in words is "six hundred forty-four million, five hundred thirty-seven thousand, four hundred eight".