138908021 has 16 divisors (see below), whose sum is σ = 161729280. Its totient is φ = 116847360.

The previous prime is 138908009. The next prime is 138908023. The reversal of 138908021 is 120809831.

It is not a de Polignac number, because 138908021 - 2¹⁴ = 138891637 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138908023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 137165 + ... + 138173.

It is an arithmetic number, because the mean of its divisors is an integer number (10108080).

Almost surely, 2^138908021 is an apocalyptic number.

It is an amenable number.

138908021 is a deficient number, since it is larger than the sum of its proper divisors (22821259).

138908021 is a wasteful number, since it uses less digits than its factorization.

138908021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1364.

The product of its (nonzero) digits is 3456, while the sum is 32.

The square root of 138908021 is about 11785.9246985546. The cubic root of 138908021 is about 517.8958624009.

The spelling of 138908021 in words is "one hundred thirty-eight million, nine hundred eight thousand, twenty-one".