138728 has 8 divisors (see below), whose sum is σ = 260130. Its totient is φ = 69360.

The previous prime is 138727. The next prime is 138731. The reversal of 138728 is 827831.

138728 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 91204 + 47524 = 302^2 + 218^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an Ulam number.

It is a self number, because there is not a number n which added to its sum of digits gives 138728.

It is not an unprimeable number, because it can be changed into a prime (138727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8663 + ... + 8678.

2¹³⁸⁷²⁸ is an apocalyptic number.

It is an amenable number.

138728 is a deficient number, since it is larger than the sum of its proper divisors (121402).

138728 is a wasteful number, since it uses less digits than its factorization.

138728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17347 (or 17343 counting only the distinct ones).

The product of its digits is 2688, while the sum is 29.

The square root of 138728 is about 372.4620786067. The cubic root of 138728 is about 51.7672039388.

The spelling of 138728 in words is "one hundred thirty-eight thousand, seven hundred twenty-eight".