18373921 has 2 divisors, whose sum is σ = 18373922. Its totient is φ = 18373920.

The previous prime is 18373919. The next prime is 18373939. The reversal of 18373921 is 12937381.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17139600 + 1234321 = 4140^2 + 1111^2 .

It is an emirp because it is prime and its reverse (12937381) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18373921 - 2¹ = 18373919 is a prime.

Together with 18373919, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (18373981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9186960 + 9186961.

It is an arithmetic number, because the mean of its divisors is an integer number (9186961).

Almost surely, 2^18373921 is an apocalyptic number.

It is an amenable number.

18373921 is a deficient number, since it is larger than the sum of its proper divisors (1).

18373921 is an equidigital number, since it uses as much as digits as its factorization.

18373921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9072, while the sum is 34.

The square root of 18373921 is about 4286.4811909071. The cubic root of 18373921 is about 263.8764391558.

The spelling of 18373921 in words is "eighteen million, three hundred seventy-three thousand, nine hundred twenty-one".