644326553 has 16 divisors (see below), whose sum is σ = 720921600. Its totient is φ = 571771200.

The previous prime is 644326549. The next prime is 644326559. The reversal of 644326553 is 355623446.

It is a happy number.

644326553 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 644326553 - 2² = 644326549 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644326559) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 86528 + ... + 93678.

It is an arithmetic number, because the mean of its divisors is an integer number (45057600).

Almost surely, 2^644326553 is an apocalyptic number.

It is an amenable number.

644326553 is a deficient number, since it is larger than the sum of its proper divisors (76595047).

644326553 is a wasteful number, since it uses less digits than its factorization.

644326553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7432.

The product of its digits is 259200, while the sum is 38.

The square root of 644326553 is about 25383.5882609217. The cubic root of 644326553 is about 863.7114488712.

Adding to 644326553 its reverse (355623446), we get a palindrome (999949999).

The spelling of 644326553 in words is "six hundred forty-four million, three hundred twenty-six thousand, five hundred fifty-three".