18845221 has 2 divisors, whose sum is σ = 18845222. Its totient is φ = 18845220.

The previous prime is 18845201. The next prime is 18845227. The reversal of 18845221 is 12254881.

18845221 = T₃₅₄₃ + T₃₅₄₄ + T₃₅₄₅.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15100996 + 3744225 = 3886^2 + 1935^2 .

It is a cyclic number.

It is not a de Polignac number, because 18845221 - 2¹⁷ = 18714149 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18845227) 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, 9422610 + 9422611.

It is an arithmetic number, because the mean of its divisors is an integer number (9422611).

Almost surely, 2^18845221 is an apocalyptic number.

18845221 is the 3545-th centered triangular number.

It is an amenable number.

18845221 is a deficient number, since it is larger than the sum of its proper divisors (1).

18845221 is an equidigital number, since it uses as much as digits as its factorization.

18845221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5120, while the sum is 31.

The square root of 18845221 is about 4341.1082686337. The cubic root of 18845221 is about 266.1136049686.

The spelling of 18845221 in words is "eighteen million, eight hundred forty-five thousand, two hundred twenty-one".