18618221 has 2 divisors, whose sum is σ = 18618222. Its totient is φ = 18618220.

The previous prime is 18618209. The next prime is 18618227. The reversal of 18618221 is 12281681.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10432900 + 8185321 = 3230^2 + 2861^2 .

It is a cyclic number.

It is not a de Polignac number, because 18618221 - 2¹⁰ = 18617197 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18618227) 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, 9309110 + 9309111.

It is an arithmetic number, because the mean of its divisors is an integer number (9309111).

Almost surely, 2^18618221 is an apocalyptic number.

It is an amenable number.

18618221 is a deficient number, since it is larger than the sum of its proper divisors (1).

18618221 is an equidigital number, since it uses as much as digits as its factorization.

18618221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1536, while the sum is 29.

The square root of 18618221 is about 4314.8836600771. The cubic root of 18618221 is about 265.0407959027.

It can be divided in two parts, 186 and 18221, that multiplied together give a triangular number (3389106 = T₂₆₀₃).

The spelling of 18618221 in words is "eighteen million, six hundred eighteen thousand, two hundred twenty-one".