138921 has 4 divisors (see below), whose sum is σ = 185232. Its totient is φ = 92612.

The previous prime is 138917. The next prime is 138923. The reversal of 138921 is 129831.

138921 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 a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 138921 - 2² = 138917 is a prime.

It is a D-number.

It is a plaindrome in base 14.

It is a junction number, because it is equal to n+sod(n) for n = 138891 and 138900.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 138921.

It is not an unprimeable number, because it can be changed into a prime (138923) 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, 23151 + ... + 23156.

It is an arithmetic number, because the mean of its divisors is an integer number (46308).

2¹³⁸⁹²¹ is an apocalyptic number.

It is an amenable number.

138921 is a deficient number, since it is larger than the sum of its proper divisors (46311).

138921 is an equidigital number, since it uses as much as digits as its factorization.

138921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46310.

The product of its digits is 432, while the sum is 24.

The square root of 138921 is about 372.7210753365. The cubic root of 138921 is about 51.7911991926.

The spelling of 138921 in words is "one hundred thirty-eight thousand, nine hundred twenty-one".