138665 has 4 divisors (see below), whose sum is σ = 166404. Its totient is φ = 110928.

The previous prime is 138661. The next prime is 138679. The reversal of 138665 is 566831.

138665 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 566831 = 17 ⋅33343.

It can be written as a sum of positive squares in 2 ways, for example, as 38809 + 99856 = 197^2 + 316^2 .

It is a cyclic number.

It is not a de Polignac number, because 138665 - 2² = 138661 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (138661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13862 + ... + 13871.

It is an arithmetic number, because the mean of its divisors is an integer number (41601).

2¹³⁸⁶⁶⁵ is an apocalyptic number.

It is an amenable number.

138665 is a deficient number, since it is larger than the sum of its proper divisors (27739).

138665 is an equidigital number, since it uses as much as digits as its factorization.

138665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27738.

The product of its digits is 4320, while the sum is 29.

The square root of 138665 is about 372.3774966348. The cubic root of 138665 is about 51.7593664735.

The spelling of 138665 in words is "one hundred thirty-eight thousand, six hundred sixty-five".