18821945521 has 2 divisors, whose sum is σ = 18821945522. Its totient is φ = 18821945520.

The previous prime is 18821945497. The next prime is 18821945561. The reversal of 18821945521 is 12554912881.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18703571121 + 118374400 = 136761^2 + 10880^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18821945521 is a prime.

It is a super-2 number, since 2×18821945521² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (18821945561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9410972760 + 9410972761.

It is an arithmetic number, because the mean of its divisors is an integer number (9410972761).

Almost surely, 2^18821945521 is an apocalyptic number.

It is an amenable number.

18821945521 is a deficient number, since it is larger than the sum of its proper divisors (1).

18821945521 is an equidigital number, since it uses as much as digits as its factorization.

18821945521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 230400, while the sum is 46.

The spelling of 18821945521 in words is "eighteen billion, eight hundred twenty-one million, nine hundred forty-five thousand, five hundred twenty-one".