644000557 has 8 divisors (see below), whose sum is σ = 653385600. Its totient is φ = 634671744.

The previous prime is 644000549. The next prime is 644000563. The reversal of 644000557 is 755000446.

It is a happy number.

644000557 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 644000557 - 2³ = 644000549 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644000657) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9294 + ... + 37072.

It is an arithmetic number, because the mean of its divisors is an integer number (81673200).

Almost surely, 2^644000557 is an apocalyptic number.

It is an amenable number.

644000557 is a deficient number, since it is larger than the sum of its proper divisors (9385043).

644000557 is a wasteful number, since it uses less digits than its factorization.

644000557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28115.

The product of its (nonzero) digits is 16800, while the sum is 31.

The square root of 644000557 is about 25377.1660553341. The cubic root of 644000557 is about 863.5657598177.

The spelling of 644000557 in words is "six hundred forty-four million, five hundred fifty-seven", and thus it is an aban number.