638754921 has 24 divisors (see below), whose sum is σ = 1055658240. Its totient is φ = 364585536.

The previous prime is 638754911. The next prime is 638754937. The reversal of 638754921 is 129457836.

638754921 is a `hidden beast` number, since 6 + 3 + 87 + 549 + 21 = 666.

It is not a de Polignac number, because 638754921 - 2¹⁰ = 638753897 is a prime.

It is not an unprimeable number, because it can be changed into a prime (638754911) by changing a digit.

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 in 23 ways as a sum of consecutive naturals, for example, 54720 + ... + 65358.

It is an arithmetic number, because the mean of its divisors is an integer number (43985760).

Almost surely, 2^638754921 is an apocalyptic number.

It is an amenable number.

638754921 is a deficient number, since it is larger than the sum of its proper divisors (416903319).

638754921 is a wasteful number, since it uses less digits than its factorization.

638754921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11605 (or 11602 counting only the distinct ones).

The product of its digits is 362880, while the sum is 45.

The square root of 638754921 is about 25273.6012669346. The cubic root of 638754921 is about 861.2146712674.

The spelling of 638754921 in words is "six hundred thirty-eight million, seven hundred fifty-four thousand, nine hundred twenty-one".