638613782664 has 128 divisors (see below), whose sum is σ = 1889341130880. Its totient is φ = 177329203200.

The previous prime is 638613782647. The next prime is 638613782669. The reversal of 638613782664 is 466287316836.

It is a junction number, because it is equal to n+sod(n) for n = 638613782598 and 638613782607.

It is not an unprimeable number, because it can be changed into a prime (638613782669) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 208927 + ... + 1149294.

It is an arithmetic number, because the mean of its divisors is an integer number (14760477585).

Almost surely, 2^638613782664 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 638613782664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (944670565440).

638613782664 is an abundant number, since it is smaller than the sum of its proper divisors (1250727348216).

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

638613782664 is a wasteful number, since it uses less digits than its factorization.

638613782664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1358391 (or 1358387 counting only the distinct ones).

The product of its digits is 41803776, while the sum is 60.

The spelling of 638613782664 in words is "six hundred thirty-eight billion, six hundred thirteen million, seven hundred eighty-two thousand, six hundred sixty-four".