18431381 has 2 divisors, whose sum is σ = 18431382. Its totient is φ = 18431380.

The previous prime is 18431377. The next prime is 18431431. The reversal of 18431381 is 18313481.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17724100 + 707281 = 4210^2 + 841^2 .

It is a cyclic number.

It is not a de Polignac number, because 18431381 - 2² = 18431377 is a prime.

It is a super-2 number, since 2×18431381² = 679431611134322, which contains 22 as substring.

It is equal to p_1177094 and since 18431381 and 1177094 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18431341) 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 as a sum of consecutive naturals, namely, 9215690 + 9215691.

It is an arithmetic number, because the mean of its divisors is an integer number (9215691).

Almost surely, 2^18431381 is an apocalyptic number.

It is an amenable number.

18431381 is a deficient number, since it is larger than the sum of its proper divisors (1).

18431381 is an equidigital number, since it uses as much as digits as its factorization.

18431381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2304, while the sum is 29.

The square root of 18431381 is about 4293.1784262944. The cubic root of 18431381 is about 264.1512228574.

The spelling of 18431381 in words is "eighteen million, four hundred thirty-one thousand, three hundred eighty-one".