21108361 has 2 divisors, whose sum is σ = 21108362. Its totient is φ = 21108360.

The previous prime is 21108359. The next prime is 21108377. The reversal of 21108361 is 16380112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19713600 + 1394761 = 4440^2 + 1181^2 .

It is a cyclic number.

It is not a de Polignac number, because 21108361 - 2¹ = 21108359 is a prime.

Together with 21108359, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21108301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10554180 + 10554181.

It is an arithmetic number, because the mean of its divisors is an integer number (10554181).

Almost surely, 2^21108361 is an apocalyptic number.

It is an amenable number.

21108361 is a deficient number, since it is larger than the sum of its proper divisors (1).

21108361 is an equidigital number, since it uses as much as digits as its factorization.

21108361 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 288, while the sum is 22.

The square root of 21108361 is about 4594.3836365719. The cubic root of 21108361 is about 276.3661430923.

Adding to 21108361 its reverse (16380112), we get a palindrome (37488473).

The spelling of 21108361 in words is "twenty-one million, one hundred eight thousand, three hundred sixty-one".