18864221 has 2 divisors, whose sum is σ = 18864222. Its totient is φ = 18864220.

The previous prime is 18864217. The next prime is 18864253. The reversal of 18864221 is 12246881.

It is a happy number.

It is an a-pointer prime, because the next prime (18864253) can be obtained adding 18864221 to its sum of digits (32).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13980121 + 4884100 = 3739^2 + 2210^2 .

It is an emirp because it is prime and its reverse (12246881) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18864221 - 2² = 18864217 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18864211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9432110 + 9432111.

It is an arithmetic number, because the mean of its divisors is an integer number (9432111).

Almost surely, 2^18864221 is an apocalyptic number.

It is an amenable number.

18864221 is a deficient number, since it is larger than the sum of its proper divisors (1).

18864221 is an equidigital number, since it uses as much as digits as its factorization.

18864221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6144, while the sum is 32.

The square root of 18864221 is about 4343.2960985869. The cubic root of 18864221 is about 266.2030080100.

The spelling of 18864221 in words is "eighteen million, eight hundred sixty-four thousand, two hundred twenty-one".