138639428 has 24 divisors (see below), whose sum is σ = 258995520. Its totient is φ = 64743840.

The previous prime is 138639419. The next prime is 138639443. The reversal of 138639428 is 824936831.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7451 + ... + 18242.

It is an arithmetic number, because the mean of its divisors is an integer number (10791480).

Almost surely, 2^138639428 is an apocalyptic number.

It is an amenable number.

138639428 is a deficient number, since it is larger than the sum of its proper divisors (120356092).

138639428 is a wasteful number, since it uses less digits than its factorization.

138639428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25787 (or 25785 counting only the distinct ones).

The product of its digits is 248832, while the sum is 44.

The square root of 138639428 is about 11774.5245339249. The cubic root of 138639428 is about 517.5618453163.

The spelling of 138639428 in words is "one hundred thirty-eight million, six hundred thirty-nine thousand, four hundred twenty-eight".