18185521 has 2 divisors, whose sum is σ = 18185522. Its totient is φ = 18185520.

The previous prime is 18185507. The next prime is 18185539. The reversal of 18185521 is 12558181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9541921 + 8643600 = 3089^2 + 2940^2 .

It is a cyclic number.

It is not a de Polignac number, because 18185521 - 2⁹ = 18185009 is a prime.

It is not a weakly prime, because it can be changed into another prime (18185021) 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, 9092760 + 9092761.

It is an arithmetic number, because the mean of its divisors is an integer number (9092761).

Almost surely, 2^18185521 is an apocalyptic number.

It is an amenable number.

18185521 is a deficient number, since it is larger than the sum of its proper divisors (1).

18185521 is an equidigital number, since it uses as much as digits as its factorization.

18185521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3200, while the sum is 31.

The square root of 18185521 is about 4264.4484989269. The cubic root of 18185521 is about 262.9714388257.

The spelling of 18185521 in words is "eighteen million, one hundred eighty-five thousand, five hundred twenty-one".