18398021 has 2 divisors, whose sum is σ = 18398022. Its totient is φ = 18398020.

The previous prime is 18398011. The next prime is 18398069. The reversal of 18398021 is 12089381.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18395521 + 2500 = 4289^2 + 50^2 .

It is an emirp because it is prime and its reverse (12089381) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18398021 - 2⁶ = 18397957 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18398011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9199010 + 9199011.

It is an arithmetic number, because the mean of its divisors is an integer number (9199011).

Almost surely, 2^18398021 is an apocalyptic number.

It is an amenable number.

18398021 is a deficient number, since it is larger than the sum of its proper divisors (1).

18398021 is an equidigital number, since it uses as much as digits as its factorization.

18398021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3456, while the sum is 32.

The square root of 18398021 is about 4289.2914333256. The cubic root of 18398021 is about 263.9917591933.

The spelling of 18398021 in words is "eighteen million, three hundred ninety-eight thousand, twenty-one".