18320221 has 2 divisors, whose sum is σ = 18320222. Its totient is φ = 18320220.

The previous prime is 18320209. The next prime is 18320227. The reversal of 18320221 is 12202381.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14364100 + 3956121 = 3790^2 + 1989^2 .

It is an emirp because it is prime and its reverse (12202381) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18320221 - 2⁵ = 18320189 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18320227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9160110 + 9160111.

It is an arithmetic number, because the mean of its divisors is an integer number (9160111).

Almost surely, 2^18320221 is an apocalyptic number.

It is an amenable number.

18320221 is a deficient number, since it is larger than the sum of its proper divisors (1).

18320221 is an equidigital number, since it uses as much as digits as its factorization.

18320221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 192, while the sum is 19.

The square root of 18320221 is about 4280.2127283583. The cubic root of 18320221 is about 263.6191180698.

The spelling of 18320221 in words is "eighteen million, three hundred twenty thousand, two hundred twenty-one".