644906859968 has 28 divisors (see below), whose sum is σ = 1462556629872. Its totient is φ = 276388654080.

The previous prime is 644906859943. The next prime is 644906859997. The reversal of 644906859968 is 869958609446.

It is a happy number.

644906859968 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (28).

It is a super-2 number, since 2×644906859968² (a number of 24 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 644906859895 and 644906859904.

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, 719761673 + ... + 719762568.

Almost surely, 2^644906859968 is an apocalyptic number.

It is an amenable number.

644906859968 is an abundant number, since it is smaller than the sum of its proper divisors (817649769904).

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

644906859968 is a wasteful number, since it uses less digits than its factorization.

644906859968 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1439524260 (or 1439524250 counting only the distinct ones).

The product of its (nonzero) digits is 806215680, while the sum is 74.

The spelling of 644906859968 in words is "six hundred forty-four billion, nine hundred six million, eight hundred fifty-nine thousand, nine hundred sixty-eight".