638636580864 has 336 divisors, whose sum is σ = 1879548194160. Its totient is φ = 208915660800.

The previous prime is 638636580863. The next prime is 638636580929. The reversal of 638636580864 is 468085636836.

638636580864 is a `hidden beast` number, since 63 + 86 + 365 + 80 + 8 + 64 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638636580863) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1035067084 + ... + 1035067700.

It is an arithmetic number, because the mean of its divisors is an integer number (5593893435).

Almost surely, 2^638636580864 is an apocalyptic number.

638636580864 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 638636580864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (939774097080).

638636580864 is an abundant number, since it is smaller than the sum of its proper divisors (1240911613296).

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

638636580864 is a wasteful number, since it uses less digits than its factorization.

638636580864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 889 (or 862 counting only the distinct ones).

The product of its (nonzero) digits is 119439360, while the sum is 63.

The spelling of 638636580864 in words is "six hundred thirty-eight billion, six hundred thirty-six million, five hundred eighty thousand, eight hundred sixty-four".