138121 has 4 divisors (see below), whose sum is σ = 141892. Its totient is φ = 134352.

The previous prime is 138113. The next prime is 138139. The reversal of 138121 is 121831.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 121831 = 23 ⋅5297.

It can be written as a sum of positive squares in 2 ways, for example, as 102400 + 35721 = 320^2 + 189^2 .

It is a cyclic number.

It is not a de Polignac number, because 138121 - 2³ = 138113 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 138095 and 138104.

It is not an unprimeable number, because it can be changed into a prime (138101) 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, 1830 + ... + 1903.

It is an arithmetic number, because the mean of its divisors is an integer number (35473).

2¹³⁸¹²¹ is an apocalyptic number.

It is an amenable number.

138121 is a deficient number, since it is larger than the sum of its proper divisors (3771).

138121 is an equidigital number, since it uses as much as digits as its factorization.

138121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3770.

The product of its digits is 48, while the sum is 16.

The square root of 138121 is about 371.6463372616. The cubic root of 138121 is about 51.6915916274.

Adding to 138121 its reverse (121831), we get a palindrome (259952).

Subtracting from 138121 its reverse (121831), we obtain a triangular number (16290 = T₁₈₀).

The spelling of 138121 in words is "one hundred thirty-eight thousand, one hundred twenty-one".