21616623503521 has 2 divisors, whose sum is σ = 21616623503522. Its totient is φ = 21616623503520.

The previous prime is 21616623503509. The next prime is 21616623503591. The reversal of 21616623503521 is 12530532661612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12332633886225 + 9283989617296 = 3511785^2 + 3046964^2 .

It is a cyclic number.

It is not a de Polignac number, because 21616623503521 - 2¹⁵ = 21616623470753 is a prime.

It is not a weakly prime, because it can be changed into another prime (21616623503591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10808311751760 + 10808311751761.

It is an arithmetic number, because the mean of its divisors is an integer number (10808311751761).

Almost surely, 2^{21616623503521} is an apocalyptic number.

It is an amenable number.

21616623503521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21616623503521 is an equidigital number, since it uses as much as digits as its factorization.

21616623503521 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 388800, while the sum is 43.

The spelling of 21616623503521 in words is "twenty-one trillion, six hundred sixteen billion, six hundred twenty-three million, five hundred three thousand, five hundred twenty-one".