644638108 has 12 divisors (see below), whose sum is σ = 1128307320. Its totient is φ = 322264592.

The previous prime is 644638097. The next prime is 644638109. The reversal of 644638108 is 801836446.

644638108 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644638109) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 25503 + ... + 44041.

It is an arithmetic number, because the mean of its divisors is an integer number (94025610).

Almost surely, 2^644638108 is an apocalyptic number.

It is an amenable number.

644638108 is a deficient number, since it is larger than the sum of its proper divisors (483669212).

644638108 is a wasteful number, since it uses less digits than its factorization.

644638108 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27236 (or 27234 counting only the distinct ones).

The product of its (nonzero) digits is 110592, while the sum is 40.

The square root of 644638108 is about 25389.7244569531. The cubic root of 644638108 is about 863.8506382613.

The spelling of 644638108 in words is "six hundred forty-four million, six hundred thirty-eight thousand, one hundred eight".