638634334640 has 80 divisors (see below), whose sum is σ = 1513409885568. Its totient is φ = 250582499328.

The previous prime is 638634334633. The next prime is 638634334687. The reversal of 638634334640 is 46433436836.

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 512729 + ... + 1241031.

Almost surely, 2^638634334640 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 638634334640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (756704942784).

638634334640 is an abundant number, since it is smaller than the sum of its proper divisors (874775550928).

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

638634334640 is a wasteful number, since it uses less digits than its factorization.

638634334640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 728526 (or 728520 counting only the distinct ones).

The product of its (nonzero) digits is 8957952, while the sum is 50.

The spelling of 638634334640 in words is "six hundred thirty-eight billion, six hundred thirty-four million, three hundred thirty-four thousand, six hundred forty".