18209381 has 4 divisors (see below), whose sum is σ = 18218700. Its totient is φ = 18200064.

The previous prime is 18209341. The next prime is 18209407. The reversal of 18209381 is 18390281.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 5924356 + 12285025 = 2434^2 + 3505^2 .

It is a cyclic number.

It is not a de Polignac number, because 18209381 - 2¹⁰ = 18208357 is a prime.

It is a super-2 number, since 2×18209381² = 663163112806322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18209341) 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, 476 + ... + 6053.

It is an arithmetic number, because the mean of its divisors is an integer number (4554675).

Almost surely, 2^18209381 is an apocalyptic number.

It is an amenable number.

18209381 is a deficient number, since it is larger than the sum of its proper divisors (9319).

18209381 is an equidigital number, since it uses as much as digits as its factorization.

18209381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9318.

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

The square root of 18209381 is about 4267.2451300576. The cubic root of 18209381 is about 263.0863976147.

The spelling of 18209381 in words is "eighteen million, two hundred nine thousand, three hundred eighty-one".