638903391 has 16 divisors (see below), whose sum is σ = 982502400. Its totient is φ = 361736928.

The previous prime is 638903387. The next prime is 638903449. The reversal of 638903391 is 193309836.

638903391 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 638903391 - 2² = 638903387 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638903311) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 137271 + ... + 141848.

It is an arithmetic number, because the mean of its divisors is an integer number (61406400).

Almost surely, 2^638903391 is an apocalyptic number.

638903391 is a deficient number, since it is larger than the sum of its proper divisors (343599009).

638903391 is a wasteful number, since it uses less digits than its factorization.

638903391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 279238.

The product of its (nonzero) digits is 104976, while the sum is 42.

The square root of 638903391 is about 25276.5383508106. The cubic root of 638903391 is about 861.2813920249.

The spelling of 638903391 in words is "six hundred thirty-eight million, nine hundred three thousand, three hundred ninety-one".