12821 has 2 divisors, whose sum is σ = 12822. Its totient is φ = 12820.

The previous prime is 12809. The next prime is 12823.

12821 is nontrivially palindromic in base 10.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7921 + 4900 = 89^2 + 70^2 .

It is a palprime.

It is a cyclic number.

It is not a de Polignac number, because 12821 - 2⁶ = 12757 is a prime.

It is a Sophie Germain prime.

Together with 12823, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 12796 and 12805.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (12823) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6410 + 6411.

It is an arithmetic number, because the mean of its divisors is an integer number (6411).

2¹²⁸²¹ is an apocalyptic number.

It is an amenable number.

12821 is a deficient number, since it is larger than the sum of its proper divisors (1).

12821 is an equidigital number, since it uses as much as digits as its factorization.

12821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 32, while the sum is 14.

The square root of 12821 is about 113.2298547204. The cubic root of 12821 is about 23.4049274937.

The spelling of 12821 in words is "twelve thousand, eight hundred twenty-one".