644508397 has 8 divisors (see below), whose sum is σ = 711015480. Its totient is φ = 580419840.

The previous prime is 644508379. The next prime is 644508427. The reversal of 644508397 is 793805446.

It can be written as a sum of positive squares in 4 ways, for example, as 4468996 + 640039401 = 2114^2 + 25299^2 .

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

It is a de Polignac number, because none of the positive numbers 2^k-644508397 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 (644500397) 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, 604072 + ... + 605137.

It is an arithmetic number, because the mean of its divisors is an integer number (88876935).

Almost surely, 2^644508397 is an apocalyptic number.

It is an amenable number.

644508397 is a deficient number, since it is larger than the sum of its proper divisors (66507083).

644508397 is a wasteful number, since it uses less digits than its factorization.

644508397 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1209263.

The product of its (nonzero) digits is 725760, while the sum is 46.

The square root of 644508397 is about 25387.1699289228. The cubic root of 644508397 is about 863.7926944088.

The spelling of 644508397 in words is "six hundred forty-four million, five hundred eight thousand, three hundred ninety-seven".