138638421 has 24 divisors (see below), whose sum is σ = 214267040. Its totient is φ = 86119200.

The previous prime is 138638413. The next prime is 138638449. The reversal of 138638421 is 124836831.

138638421 is a `hidden beast` number, since 13 + 8 + 638 + 4 + 2 + 1 = 666.

It is not a de Polignac number, because 138638421 - 2³ = 138638413 is a prime.

It is a super-2 number, since 2×138638421² = 38441223554746482, which contains 22 as substring.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138638491) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3786 + ... + 17076.

Almost surely, 2^138638421 is an apocalyptic number.

It is an amenable number.

138638421 is a deficient number, since it is larger than the sum of its proper divisors (75628619).

138638421 is a wasteful number, since it uses less digits than its factorization.

138638421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13377 (or 13374 counting only the distinct ones).

The product of its digits is 27648, while the sum is 36.

The square root of 138638421 is about 11774.4817720357. The cubic root of 138638421 is about 517.5605922191.

The spelling of 138638421 in words is "one hundred thirty-eight million, six hundred thirty-eight thousand, four hundred twenty-one".