18398381 has 4 divisors (see below), whose sum is σ = 18847164. Its totient is φ = 17949600.

The previous prime is 18398353. The next prime is 18398417. The reversal of 18398381 is 18389381.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18389381 = 173 ⋅106297.

It can be written as a sum of positive squares in 2 ways, for example, as 7236100 + 11162281 = 2690^2 + 3341^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18398381 is a prime.

It is a super-2 number, since 2×18398381² = 677000846842322, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (41), and also a Moran number because the ratio is a prime number: 448741 = 18398381 / (1 + 8 + 3 + 9 + 8 + 3 + 8 + 1).

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18398351) 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, 224330 + ... + 224411.

It is an arithmetic number, because the mean of its divisors is an integer number (4711791).

Almost surely, 2^18398381 is an apocalyptic number.

It is an amenable number.

18398381 is a deficient number, since it is larger than the sum of its proper divisors (448783).

18398381 is an equidigital number, since it uses as much as digits as its factorization.

18398381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 448782.

The product of its digits is 41472, while the sum is 41.

The square root of 18398381 is about 4289.3333980935. Note that the first 4 decimals coincide. The cubic root of 18398381 is about 263.9934810527.

The spelling of 18398381 in words is "eighteen million, three hundred ninety-eight thousand, three hundred eighty-one".