21331361 has 2 divisors, whose sum is σ = 21331362. Its totient is φ = 21331360.

The previous prime is 21331339. The next prime is 21331363. The reversal of 21331361 is 16313312.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21022225 + 309136 = 4585^2 + 556^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21331361 is a prime.

It is a super-2 number, since 2×21331361² = 910053924224642, which contains 22 as substring.

Together with 21331363, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21331363) 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, 10665680 + 10665681.

It is an arithmetic number, because the mean of its divisors is an integer number (10665681).

Almost surely, 2^21331361 is an apocalyptic number.

It is an amenable number.

21331361 is a deficient number, since it is larger than the sum of its proper divisors (1).

21331361 is an equidigital number, since it uses as much as digits as its factorization.

21331361 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 324, while the sum is 20.

The square root of 21331361 is about 4618.5886372354. The cubic root of 21331361 is about 277.3359623546.

Adding to 21331361 its reverse (16313312), we get a palindrome (37644673).

The spelling of 21331361 in words is "twenty-one million, three hundred thirty-one thousand, three hundred sixty-one".