644045540408 has 8 divisors (see below), whose sum is σ = 1207585388280. Its totient is φ = 322022770200.

The previous prime is 644045540407. The next prime is 644045540513. The reversal of 644045540408 is 804045540446.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (8).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644045540407) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40252846268 + ... + 40252846283.

It is an arithmetic number, because the mean of its divisors is an integer number (150948173535).

Almost surely, 2^644045540408 is an apocalyptic number.

It is an amenable number.

644045540408 is a deficient number, since it is larger than the sum of its proper divisors (563539847872).

644045540408 is a wasteful number, since it uses less digits than its factorization.

644045540408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80505692557 (or 80505692553 counting only the distinct ones).

The product of its (nonzero) digits is 1228800, while the sum is 44.

The spelling of 644045540408 in words is "six hundred forty-four billion, forty-five million, five hundred forty thousand, four hundred eight".