18128381 has 2 divisors, whose sum is σ = 18128382. Its totient is φ = 18128380.

The previous prime is 18128377. The next prime is 18128401. The reversal of 18128381 is 18382181.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16605625 + 1522756 = 4075^2 + 1234^2 .

It is an emirp because it is prime and its reverse (18382181) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18128381 - 2² = 18128377 is a prime.

It is a super-2 number, since 2×18128381² = 657276395362322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18128311) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9064190 + 9064191.

It is an arithmetic number, because the mean of its divisors is an integer number (9064191).

Almost surely, 2^18128381 is an apocalyptic number.

It is an amenable number.

18128381 is a deficient number, since it is larger than the sum of its proper divisors (1).

18128381 is an equidigital number, since it uses as much as digits as its factorization.

18128381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3072, while the sum is 32.

The square root of 18128381 is about 4257.7436512782. The cubic root of 18128381 is about 262.6957258327.

The spelling of 18128381 in words is "eighteen million, one hundred twenty-eight thousand, three hundred eighty-one".