644329872388 has 18 divisors (see below), whose sum is σ = 1139229740558. Its totient is φ = 318835824000.

The previous prime is 644329872379. The next prime is 644329872409. The reversal of 644329872388 is 883278923446.

It can be written as a sum of positive squares in only one way, i.e., 538048656324 + 106281216064 = 733518^2 + 326008^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 15791013 + ... + 15831763.

Almost surely, 2^644329872388 is an apocalyptic number.

It is an amenable number.

644329872388 is a deficient number, since it is larger than the sum of its proper divisors (494899868170).

644329872388 is an frugal number, since it uses more digits than its factorization.

644329872388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81603 (or 40850 counting only the distinct ones).

The product of its digits is 111476736, while the sum is 64.

The spelling of 644329872388 in words is "six hundred forty-four billion, three hundred twenty-nine million, eight hundred seventy-two thousand, three hundred eighty-eight".