138905 has 8 divisors (see below), whose sum is σ = 179592. Its totient is φ = 102528.

The previous prime is 138899. The next prime is 138917. The reversal of 138905 is 509831.

138905 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 4 ways, for example, as 3481 + 135424 = 59^2 + 368^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 138905 - 2⁴ = 138889 is a prime.

It is a Duffinian number.

It is a plaindrome in base 14.

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, 1004 + ... + 1133.

It is an arithmetic number, because the mean of its divisors is an integer number (22449).

2¹³⁸⁹⁰⁵ is an apocalyptic number.

It is an amenable number.

138905 is a deficient number, since it is larger than the sum of its proper divisors (40687).

138905 is a wasteful number, since it uses less digits than its factorization.

138905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2155.

The product of its (nonzero) digits is 1080, while the sum is 26.

The square root of 138905 is about 372.6996109469. The cubic root of 138905 is about 51.7892107939.

The spelling of 138905 in words is "one hundred thirty-eight thousand, nine hundred five".