644666305440 has 96 divisors (see below), whose sum is σ = 2058516766656. Its totient is φ = 169556060160.

The previous prime is 644666305433. The next prime is 644666305483. The reversal of 644666305440 is 44503666446.

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

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a self number, because there is not a number n which added to its sum of digits gives 644666305440.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9163966 + ... + 9234045.

It is an arithmetic number, because the mean of its divisors is an integer number (21442882986).

Almost surely, 2^644666305440 is an apocalyptic number.

644666305440 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

644666305440 is an abundant number, since it is smaller than the sum of its proper divisors (1413850461216).

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

644666305440 is a wasteful number, since it uses less digits than its factorization.

644666305440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18398102 (or 18398094 counting only the distinct ones).

The product of its (nonzero) digits is 4976640, while the sum is 48.

The spelling of 644666305440 in words is "six hundred forty-four billion, six hundred sixty-six million, three hundred five thousand, four hundred forty".