644956638 has 8 divisors (see below), whose sum is σ = 1289913288. Its totient is φ = 214985544.

The previous prime is 644956619. The next prime is 644956667. The reversal of 644956638 is 836659446.

It is a happy number.

644956638 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.

644956638 is an admirable number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 53746381 + ... + 53746392.

It is an arithmetic number, because the mean of its divisors is an integer number (161239161).

Almost surely, 2^644956638 is an apocalyptic number.

644956638 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644956638 is a wasteful number, since it uses less digits than its factorization.

644956638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 107492778.

The product of its digits is 3732480, while the sum is 51.

The square root of 644956638 is about 25395.9964955109. The cubic root of 644956638 is about 863.9928974253.

The spelling of 644956638 in words is "six hundred forty-four million, nine hundred fifty-six thousand, six hundred thirty-eight".