644774487760 has 40 divisors (see below), whose sum is σ = 1614416123880. Its totient is φ = 238070579712.

The previous prime is 644774487737. The next prime is 644774487761. The reversal of 644774487760 is 67784477446.

It can be written as a sum of positive squares in 4 ways, for example, as 1788613264 + 642985874496 = 42292^2 + 801864^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a junction number, because it is equal to n+sod(n) for n = 644774487692 and 644774487701.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644774487761) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 309986695 + ... + 309988774.

It is an arithmetic number, because the mean of its divisors is an integer number (40360403097).

Almost surely, 2^644774487760 is an apocalyptic number.

It is an amenable number.

644774487760 is an abundant number, since it is smaller than the sum of its proper divisors (969641636120).

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

644774487760 is a wasteful number, since it uses less digits than its factorization.

644774487760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 619975495 (or 619975489 counting only the distinct ones).

The product of its (nonzero) digits is 177020928, while the sum is 64.

The spelling of 644774487760 in words is "six hundred forty-four billion, seven hundred seventy-four million, four hundred eighty-seven thousand, seven hundred sixty".