638405728 has 12 divisors (see below), whose sum is σ = 1256861340. Its totient is φ = 319202848.

The previous prime is 638405717. The next prime is 638405737. The reversal of 638405728 is 827504836.

It is a hoax number, since the sum of its digits (43) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9975058 + ... + 9975121.

It is an arithmetic number, because the mean of its divisors is an integer number (104738445).

Almost surely, 2^638405728 is an apocalyptic number.

It is an amenable number.

638405728 is a deficient number, since it is larger than the sum of its proper divisors (618455612).

638405728 is a wasteful number, since it uses less digits than its factorization.

638405728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19950189 (or 19950181 counting only the distinct ones).

The product of its (nonzero) digits is 322560, while the sum is 43.

The square root of 638405728 is about 25266.6920668298. The cubic root of 638405728 is about 861.0577070743.

The spelling of 638405728 in words is "six hundred thirty-eight million, four hundred five thousand, seven hundred twenty-eight".