644000000000 has 480 divisors, whose sum is σ = 1919531053440. Its totient is φ = 211200000000.

The previous prime is 643999999987. The next prime is 644000000047. The reversal of 644000000000 is 446.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (14).

It is a nialpdrome in base 10.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 27999999989 + ... + 28000000011.

It is an arithmetic number, because the mean of its divisors is an integer number (3999023028).

Almost surely, 2^644000000000 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644000000000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (959765526720).

644000000000 is an abundant number, since it is smaller than the sum of its proper divisors (1275531053440).

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

644000000000 is an frugal number, since it uses more digits than its factorization.

644000000000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 97 (or 37 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 14.

Adding to 644000000000 its reverse (446), we get a palindrome (644000000446).

The spelling of 644000000000 in words is "six hundred forty-four billion", and thus it is an aban number.