13221821 has 2 divisors, whose sum is σ = 13221822. Its totient is φ = 13221820.

The previous prime is 13221781. The next prime is 13221823. The reversal of 13221821 is 12812231.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 8916196 + 4305625 = 2986^2 + 2075^2 .

It is a cyclic number.

It is not a de Polignac number, because 13221821 - 2¹⁸ = 12959677 is a prime.

It is a Sophie Germain prime.

Together with 13221823, 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 = 13221793 and 13221802.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (13221823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6610910 + 6610911.

It is an arithmetic number, because the mean of its divisors is an integer number (6610911).

Almost surely, 2^13221821 is an apocalyptic number.

It is an amenable number.

13221821 is a deficient number, since it is larger than the sum of its proper divisors (1).

13221821 is an equidigital number, since it uses as much as digits as its factorization.

13221821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 192, while the sum is 20.

The square root of 13221821 is about 3636.1822011555. The cubic root of 13221821 is about 236.4633063201.

The spelling of 13221821 in words is "thirteen million, two hundred twenty-one thousand, eight hundred twenty-one".