138689 has 4 divisors (see below), whose sum is σ = 139440. Its totient is φ = 137940.

The previous prime is 138683. The next prime is 138727. The reversal of 138689 is 986831.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 986831 = 239 ⋅4129.

It is a cyclic number.

It is not a de Polignac number, because 138689 - 2⁸ = 138433 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 11.

It is not an unprimeable number, because it can be changed into a prime (138683) 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, 122 + ... + 540.

It is an arithmetic number, because the mean of its divisors is an integer number (34860).

2¹³⁸⁶⁸⁹ is an apocalyptic number.

It is an amenable number.

138689 is a deficient number, since it is larger than the sum of its proper divisors (751).

138689 is an equidigital number, since it uses as much as digits as its factorization.

138689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 750.

The product of its digits is 10368, while the sum is 35.

The square root of 138689 is about 372.4097206035. The cubic root of 138689 is about 51.7623524544.

The spelling of 138689 in words is "one hundred thirty-eight thousand, six hundred eighty-nine".