18455221 has 2 divisors, whose sum is σ = 18455222. Its totient is φ = 18455220.

The previous prime is 18455219. The next prime is 18455249. The reversal of 18455221 is 12255481.

It is an a-pointer prime, because the next prime (18455249) can be obtained adding 18455221 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15602500 + 2852721 = 3950^2 + 1689^2 .

It is a cyclic number.

It is not a de Polignac number, because 18455221 - 2¹ = 18455219 is a prime.

Together with 18455219, it forms a pair of twin primes.

It is equal to p_1178524 and since 18455221 and 1178524 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18455221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18455201) 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, 9227610 + 9227611.

It is an arithmetic number, because the mean of its divisors is an integer number (9227611).

Almost surely, 2^18455221 is an apocalyptic number.

It is an amenable number.

18455221 is a deficient number, since it is larger than the sum of its proper divisors (1).

18455221 is an equidigital number, since it uses as much as digits as its factorization.

18455221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3200, while the sum is 28.

The square root of 18455221 is about 4295.9540267559. The cubic root of 18455221 is about 264.2650622563.

The spelling of 18455221 in words is "eighteen million, four hundred fifty-five thousand, two hundred twenty-one".