138821 has 2 divisors, whose sum is σ = 138822. Its totient is φ = 138820.

The previous prime is 138799. The next prime is 138829. The reversal of 138821 is 128831.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 93025 + 45796 = 305^2 + 214^2 .

It is an emirp because it is prime and its reverse (128831) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-138821 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a nialpdrome in base 11.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 138821.

It is not a weakly prime, because it can be changed into another prime (138829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69410 + 69411.

It is an arithmetic number, because the mean of its divisors is an integer number (69411).

2¹³⁸⁸²¹ is an apocalyptic number.

It is an amenable number.

138821 is a deficient number, since it is larger than the sum of its proper divisors (1).

138821 is an equidigital number, since it uses as much as digits as its factorization.

138821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 384, while the sum is 23.

The square root of 138821 is about 372.5869026147. The cubic root of 138821 is about 51.7787691949.

It can be divided in two parts, 138 and 821, that added together give a palindrome (959).

The spelling of 138821 in words is "one hundred thirty-eight thousand, eight hundred twenty-one".