18331381 has 2 divisors, whose sum is σ = 18331382. Its totient is φ = 18331380.

The previous prime is 18331367. The next prime is 18331429. The reversal of 18331381 is 18313381.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9979281 + 8352100 = 3159^2 + 2890^2 .

It is an emirp because it is prime and its reverse (18313381) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18331381 - 2⁵ = 18331349 is a prime.

It is a super-2 number, since 2×18331381² = 672079058734322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18331301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9165690 + 9165691.

It is an arithmetic number, because the mean of its divisors is an integer number (9165691).

Almost surely, 2^18331381 is an apocalyptic number.

It is an amenable number.

18331381 is a deficient number, since it is larger than the sum of its proper divisors (1).

18331381 is an equidigital number, since it uses as much as digits as its factorization.

18331381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1728, while the sum is 28.

The square root of 18331381 is about 4281.5162034027. The cubic root of 18331381 is about 263.6726362047.

The spelling of 18331381 in words is "eighteen million, three hundred thirty-one thousand, three hundred eighty-one".