638617865680 has 80 divisors (see below), whose sum is σ = 1552058411904. Its totient is φ = 243912430080.

The previous prime is 638617865663. The next prime is 638617865701. The reversal of 638617865680 is 86568716836.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 746722 + ... + 1354558.

Almost surely, 2^638617865680 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 638617865680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (776029205952).

638617865680 is an abundant number, since it is smaller than the sum of its proper divisors (913440546224).

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

638617865680 is a wasteful number, since it uses less digits than its factorization.

638617865680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 608444 (or 608438 counting only the distinct ones).

The product of its (nonzero) digits is 69672960, while the sum is 64.

The spelling of 638617865680 in words is "six hundred thirty-eight billion, six hundred seventeen million, eight hundred sixty-five thousand, six hundred eighty".