638866108640 has 96 divisors (see below), whose sum is σ = 1531979840160. Its totient is φ = 251737196544.

The previous prime is 638866108607. The next prime is 638866108649. The reversal of 638866108640 is 46801668836.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638866108649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2911247 + ... + 3122993.

It is an arithmetic number, because the mean of its divisors is an integer number (15958123335).

Almost surely, 2^638866108640 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 638866108640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (765989920080).

638866108640 is an abundant number, since it is smaller than the sum of its proper divisors (893113731520).

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

638866108640 is a wasteful number, since it uses less digits than its factorization.

638866108640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 212044 (or 212036 counting only the distinct ones).

The product of its (nonzero) digits is 7962624, while the sum is 56.

The spelling of 638866108640 in words is "six hundred thirty-eight billion, eight hundred sixty-six million, one hundred eight thousand, six hundred forty".