644891906208 has 96 divisors (see below), whose sum is σ = 1846885501440. Its totient is φ = 195405960960.

The previous prime is 644891906161. The next prime is 644891906237. The reversal of 644891906208 is 802609198446.

It is a tau number, because it is divible by the number of its divisors (96).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25034391 + ... + 25060137.

It is an arithmetic number, because the mean of its divisors is an integer number (19238390640).

Almost surely, 2^644891906208 is an apocalyptic number.

It is an amenable number.

644891906208 is an abundant number, since it is smaller than the sum of its proper divisors (1201993595232).

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

644891906208 is a wasteful number, since it uses less digits than its factorization.

644891906208 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49490 (or 49482 counting only the distinct ones).

The product of its (nonzero) digits is 5971968, while the sum is 57.

The spelling of 644891906208 in words is "six hundred forty-four billion, eight hundred ninety-one million, nine hundred six thousand, two hundred eight".