644321640444 has 24 divisors (see below), whose sum is σ = 1503593506128. Its totient is φ = 214748688000.

The previous prime is 644321640433. The next prime is 644321640451. The reversal of 644321640444 is 444046123446.

It is a junction number, because it is equal to n+sod(n) for n = 644321640396 and 644321640405.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3042307 + ... + 3247194.

It is an arithmetic number, because the mean of its divisors is an integer number (62649729422).

Almost surely, 2^644321640444 is an apocalyptic number.

It is an amenable number.

644321640444 is an abundant number, since it is smaller than the sum of its proper divisors (859271865684).

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

644321640444 is a wasteful number, since it uses less digits than its factorization.

644321640444 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6298045 (or 6298043 counting only the distinct ones).

The product of its (nonzero) digits is 884736, while the sum is 42.

The spelling of 644321640444 in words is "six hundred forty-four billion, three hundred twenty-one million, six hundred forty thousand, four hundred forty-four".