16565740621 has 2 divisors, whose sum is σ = 16565740622. Its totient is φ = 16565740620.

The previous prime is 16565740619. The next prime is 16565740643. The reversal of 16565740621 is 12604756561.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15764058025 + 801682596 = 125555^2 + 28314^2 .

It is a cyclic number.

It is not a de Polignac number, because 16565740621 - 2¹ = 16565740619 is a prime.

Together with 16565740619, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16565720621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8282870310 + 8282870311.

It is an arithmetic number, because the mean of its divisors is an integer number (8282870311).

Almost surely, 2^16565740621 is an apocalyptic number.

It is an amenable number.

16565740621 is a deficient number, since it is larger than the sum of its proper divisors (1).

16565740621 is an equidigital number, since it uses as much as digits as its factorization.

16565740621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 302400, while the sum is 43.

The spelling of 16565740621 in words is "sixteen billion, five hundred sixty-five million, seven hundred forty thousand, six hundred twenty-one".