21330161 has 2 divisors, whose sum is σ = 21330162. Its totient is φ = 21330160.

The previous prime is 21330157. The next prime is 21330163. The reversal of 21330161 is 16103312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17977600 + 3352561 = 4240^2 + 1831^2 .

It is a cyclic number.

It is not a de Polignac number, because 21330161 - 2² = 21330157 is a prime.

It is a Sophie Germain prime.

Together with 21330163, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21330163) 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, 10665080 + 10665081.

It is an arithmetic number, because the mean of its divisors is an integer number (10665081).

Almost surely, 2^21330161 is an apocalyptic number.

It is an amenable number.

21330161 is a deficient number, since it is larger than the sum of its proper divisors (1).

21330161 is an equidigital number, since it uses as much as digits as its factorization.

21330161 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 108, while the sum is 17.

The square root of 21330161 is about 4618.4587255923. The cubic root of 21330161 is about 277.3307617270.

Adding to 21330161 its reverse (16103312), we get a palindrome (37433473).

The spelling of 21330161 in words is "twenty-one million, three hundred thirty thousand, one hundred sixty-one".