644362640000 has 80 divisors (see below), whose sum is σ = 1604100718770. Its totient is φ = 257745024000.

The previous prime is 644362639997. The next prime is 644362640101. The reversal of 644362640000 is 46263446.

It can be written as a sum of positive squares in 5 ways, for example, as 145734589504 + 498628050496 = 381752^2 + 706136^2 .

It is a tau number, because it is divible by the number of its divisors (80).

It is a hoax number, since the sum of its digits (35) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 3947267 + ... + 4107266.

Almost surely, 2^644362640000 is an apocalyptic number.

It is an amenable number.

644362640000 is an abundant number, since it is smaller than the sum of its proper divisors (959738078770).

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

644362640000 is an frugal number, since it uses more digits than its factorization.

644362640000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8054567 (or 8054540 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 35.

The spelling of 644362640000 in words is "six hundred forty-four billion, three hundred sixty-two million, six hundred forty thousand".