18240221 has 2 divisors, whose sum is σ = 18240222. Its totient is φ = 18240220.

The previous prime is 18240191. The next prime is 18240227. The reversal of 18240221 is 12204281.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18156121 + 84100 = 4261^2 + 290^2 .

It is an emirp because it is prime and its reverse (12204281) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18240221 - 2¹⁰ = 18239197 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 18240193 and 18240202.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18240227) 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, 9120110 + 9120111.

It is an arithmetic number, because the mean of its divisors is an integer number (9120111).

Almost surely, 2^18240221 is an apocalyptic number.

It is an amenable number.

18240221 is a deficient number, since it is larger than the sum of its proper divisors (1).

18240221 is an equidigital number, since it uses as much as digits as its factorization.

18240221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 256, while the sum is 20.

The square root of 18240221 is about 4270.8571739172. The cubic root of 18240221 is about 263.2348377388.

The spelling of 18240221 in words is "eighteen million, two hundred forty thousand, two hundred twenty-one".