16663203521 has 2 divisors, whose sum is σ = 16663203522. Its totient is φ = 16663203520.

The previous prime is 16663203481. The next prime is 16663203527. The reversal of 16663203521 is 12530236661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9592243600 + 7070959921 = 97940^2 + 84089^2 .

It is an emirp because it is prime and its reverse (12530236661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 16663203521 - 2⁶ = 16663203457 is a prime.

It is not a weakly prime, because it can be changed into another prime (16663203527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8331601760 + 8331601761.

It is an arithmetic number, because the mean of its divisors is an integer number (8331601761).

Almost surely, 2^16663203521 is an apocalyptic number.

It is an amenable number.

16663203521 is a deficient number, since it is larger than the sum of its proper divisors (1).

16663203521 is an equidigital number, since it uses as much as digits as its factorization.

16663203521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 38880, while the sum is 35.

The spelling of 16663203521 in words is "sixteen billion, six hundred sixty-three million, two hundred three thousand, five hundred twenty-one".