18381421 has 4 divisors (see below), whose sum is σ = 18396832. Its totient is φ = 18366012.

The previous prime is 18381397. The next prime is 18381457. The reversal of 18381421 is 12418381.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18381421 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 18381421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18381491) 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 in 3 ways as a sum of consecutive naturals, for example, 5751 + ... + 8356.

It is an arithmetic number, because the mean of its divisors is an integer number (4599208).

Almost surely, 2^18381421 is an apocalyptic number.

It is an amenable number.

18381421 is a deficient number, since it is larger than the sum of its proper divisors (15411).

18381421 is a wasteful number, since it uses less digits than its factorization.

18381421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15410.

The product of its digits is 1536, while the sum is 28.

The square root of 18381421 is about 4287.3559451018. The cubic root of 18381421 is about 263.9123379364.

The spelling of 18381421 in words is "eighteen million, three hundred eighty-one thousand, four hundred twenty-one".