18809521 has 2 divisors, whose sum is σ = 18809522. Its totient is φ = 18809520.

The previous prime is 18809519. The next prime is 18809597. The reversal of 18809521 is 12590881.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17106496 + 1703025 = 4136^2 + 1305^2 .

It is an emirp because it is prime and its reverse (12590881) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18809521 - 2¹ = 18809519 is a prime.

Together with 18809519, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (18809321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9404760 + 9404761.

It is an arithmetic number, because the mean of its divisors is an integer number (9404761).

Almost surely, 2^18809521 is an apocalyptic number.

It is an amenable number.

18809521 is a deficient number, since it is larger than the sum of its proper divisors (1).

18809521 is an equidigital number, since it uses as much as digits as its factorization.

18809521 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5760, while the sum is 34.

The square root of 18809521 is about 4336.9944662174. The cubic root of 18809521 is about 265.9454586952.

The spelling of 18809521 in words is "eighteen million, eight hundred nine thousand, five hundred twenty-one".