21335861 has 2 divisors, whose sum is σ = 21335862. Its totient is φ = 21335860.

The previous prime is 21335857. The next prime is 21335863. The reversal of 21335861 is 16853312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21298225 + 37636 = 4615^2 + 194^2 .

It is a cyclic number.

It is not a de Polignac number, because 21335861 - 2² = 21335857 is a prime.

It is a super-2 number, since 2×21335861² = 910437929222642, which contains 22 as substring.

Together with 21335863, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21335863) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10667930 + 10667931.

It is an arithmetic number, because the mean of its divisors is an integer number (10667931).

Almost surely, 2^21335861 is an apocalyptic number.

It is an amenable number.

21335861 is a deficient number, since it is larger than the sum of its proper divisors (1).

21335861 is an equidigital number, since it uses as much as digits as its factorization.

21335861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 29.

The square root of 21335861 is about 4619.0757733555. The cubic root of 21335861 is about 277.3554629713.

The spelling of 21335861 in words is "twenty-one million, three hundred thirty-five thousand, eight hundred sixty-one".