21335813 has 2 divisors, whose sum is σ = 21335814. Its totient is φ = 21335812.

The previous prime is 21335801. The next prime is 21335819. The reversal of 21335813 is 31853312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20948929 + 386884 = 4577^2 + 622^2 .

It is a cyclic number.

It is not a de Polignac number, because 21335813 - 2⁶ = 21335749 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21335819) 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, 10667906 + 10667907.

It is an arithmetic number, because the mean of its divisors is an integer number (10667907).

Almost surely, 2^21335813 is an apocalyptic number.

It is an amenable number.

21335813 is a deficient number, since it is larger than the sum of its proper divisors (1).

21335813 is an equidigital number, since it uses as much as digits as its factorization.

21335813 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2160, while the sum is 26.

The square root of 21335813 is about 4619.0705775080. The cubic root of 21335813 is about 277.3552549792.

The spelling of 21335813 in words is "twenty-one million, three hundred thirty-five thousand, eight hundred thirteen".