21365025441521 has 2 divisors, whose sum is σ = 21365025441522. Its totient is φ = 21365025441520.

The previous prime is 21365025441509. The next prime is 21365025441553. The reversal of 21365025441521 is 12514452056312.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21127481303296 + 237544138225 = 4596464^2 + 487385^2 .

It is a cyclic number.

It is not a de Polignac number, because 21365025441521 - 2¹⁰ = 21365025440497 is a prime.

It is not a weakly prime, because it can be changed into another prime (21365025941521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10682512720760 + 10682512720761.

It is an arithmetic number, because the mean of its divisors is an integer number (10682512720761).

Almost surely, 2^{21365025441521} is an apocalyptic number.

It is an amenable number.

21365025441521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21365025441521 is an equidigital number, since it uses as much as digits as its factorization.

21365025441521 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 288000, while the sum is 41.

Adding to 21365025441521 its reverse (12514452056312), we get a palindrome (33879477497833).

The spelling of 21365025441521 in words is "twenty-one trillion, three hundred sixty-five billion, twenty-five million, four hundred forty-one thousand, five hundred twenty-one".