18989381 has 2 divisors, whose sum is σ = 18989382. Its totient is φ = 18989380.

The previous prime is 18989353. The next prime is 18989387. The reversal of 18989381 is 18398981.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15249025 + 3740356 = 3905^2 + 1934^2 .

It is a cyclic number.

It is not a de Polignac number, because 18989381 - 2¹⁰ = 18988357 is a prime.

It is a super-2 number, since 2×18989381² = 721193181526322, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18989387) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9494690 + 9494691.

It is an arithmetic number, because the mean of its divisors is an integer number (9494691).

Almost surely, 2^18989381 is an apocalyptic number.

It is an amenable number.

18989381 is a deficient number, since it is larger than the sum of its proper divisors (1).

18989381 is an equidigital number, since it uses as much as digits as its factorization.

18989381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 124416, while the sum is 47.

The square root of 18989381 is about 4357.6806904591. The cubic root of 18989381 is about 266.7904437535.

The spelling of 18989381 in words is "eighteen million, nine hundred eighty-nine thousand, three hundred eighty-one".