21663204232361 has 2 divisors, whose sum is σ = 21663204232362. Its totient is φ = 21663204232360.

The previous prime is 21663204232357. The next prime is 21663204232363. The reversal of 21663204232361 is 16323240236612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14292603669136 + 7370600563225 = 3780556^2 + 2714885^2 .

It is a cyclic number.

It is not a de Polignac number, because 21663204232361 - 2² = 21663204232357 is a prime.

It is a super-2 number, since 2×21663204232361² (a number of 27 digits) contains 22 as substring.

Together with 21663204232363, 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 (21663204232363) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10831602116180 + 10831602116181.

It is an arithmetic number, because the mean of its divisors is an integer number (10831602116181).

Almost surely, 2^{21663204232361} is an apocalyptic number.

It is an amenable number.

21663204232361 is a deficient number, since it is larger than the sum of its proper divisors (1).

21663204232361 is an equidigital number, since it uses as much as digits as its factorization.

21663204232361 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 373248, while the sum is 41.

Adding to 21663204232361 its reverse (16323240236612), we get a palindrome (37986444468973).

The spelling of 21663204232361 in words is "twenty-one trillion, six hundred sixty-three billion, two hundred four million, two hundred thirty-two thousand, three hundred sixty-one".