138918639 has 4 divisors (see below), whose sum is σ = 185224856. Its totient is φ = 92612424.

The previous prime is 138918629. The next prime is 138918649. The reversal of 138918639 is 936819831.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (138918629) and next prime (138918649).

It is not a de Polignac number, because 138918639 - 2⁵ = 138918607 is a prime.

It is a super-2 number, since 2×138918639² = 38596776523224642, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138918629) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23153104 + ... + 23153109.

It is an arithmetic number, because the mean of its divisors is an integer number (46306214).

Almost surely, 2^138918639 is an apocalyptic number.

138918639 is a deficient number, since it is larger than the sum of its proper divisors (46306217).

138918639 is an equidigital number, since it uses as much as digits as its factorization.

138918639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46306216.

The product of its digits is 279936, while the sum is 48.

The square root of 138918639 is about 11786.3751425109. The cubic root of 138918639 is about 517.9090578908.

The spelling of 138918639 in words is "one hundred thirty-eight million, nine hundred eighteen thousand, six hundred thirty-nine".