21332821 has 2 divisors, whose sum is σ = 21332822. Its totient is φ = 21332820.

The previous prime is 21332819. The next prime is 21332837. The reversal of 21332821 is 12823312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21298225 + 34596 = 4615^2 + 186^2 .

It is a cyclic number.

It is not a de Polignac number, because 21332821 - 2¹ = 21332819 is a prime.

Together with 21332819, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21332792 and 21332801.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21332881) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10666410 + 10666411.

It is an arithmetic number, because the mean of its divisors is an integer number (10666411).

Almost surely, 2^21332821 is an apocalyptic number.

It is an amenable number.

21332821 is a deficient number, since it is larger than the sum of its proper divisors (1).

21332821 is an equidigital number, since it uses as much as digits as its factorization.

21332821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 576, while the sum is 22.

The square root of 21332821 is about 4618.7466914738. The cubic root of 21332821 is about 277.3422895219.

The spelling of 21332821 in words is "twenty-one million, three hundred thirty-two thousand, eight hundred twenty-one".