18221381 has 4 divisors (see below), whose sum is σ = 18239232. Its totient is φ = 18203532.

The previous prime is 18221341. The next prime is 18221389. The reversal of 18221381 is 18312281.

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 not a de Polignac number, because 18221381 - 2¹⁰ = 18220357 is a prime.

It is a super-2 number, since 2×18221381² = 664037451094322, which contains 22 as substring.

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 18221381.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18221389) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7295 + ... + 9468.

It is an arithmetic number, because the mean of its divisors is an integer number (4559808).

Almost surely, 2^18221381 is an apocalyptic number.

It is an amenable number.

18221381 is a deficient number, since it is larger than the sum of its proper divisors (17851).

18221381 is a wasteful number, since it uses less digits than its factorization.

18221381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17850.

The product of its digits is 768, while the sum is 26.

The square root of 18221381 is about 4268.6509578554. The cubic root of 18221381 is about 263.1441763228.

The spelling of 18221381 in words is "eighteen million, two hundred twenty-one thousand, three hundred eighty-one".