18338921 has 2 divisors, whose sum is σ = 18338922. Its totient is φ = 18338920.

The previous prime is 18338867. The next prime is 18338951. The reversal of 18338921 is 12983381.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13213225 + 5125696 = 3635^2 + 2264^2 .

It is an emirp because it is prime and its reverse (12983381) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18338921 - 2¹⁰ = 18337897 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (18338951) 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, 9169460 + 9169461.

It is an arithmetic number, because the mean of its divisors is an integer number (9169461).

Almost surely, 2^18338921 is an apocalyptic number.

It is an amenable number.

18338921 is a deficient number, since it is larger than the sum of its proper divisors (1).

18338921 is an equidigital number, since it uses as much as digits as its factorization.

18338921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10368, while the sum is 35.

The square root of 18338921 is about 4282.3966420686. The cubic root of 18338921 is about 263.7087822205.

The spelling of 18338921 in words is "eighteen million, three hundred thirty-eight thousand, nine hundred twenty-one".