18438381 has 32 divisors (see below), whose sum is σ = 29715840. Its totient is φ = 11232000.

The previous prime is 18438373. The next prime is 18438383. The reversal of 18438381 is 18383481.

It is not a de Polignac number, because 18438381 - 2³ = 18438373 is a prime.

It is a super-2 number, since 2×18438381² = 679947787802322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18438383) 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 31 ways as a sum of consecutive naturals, for example, 45781 + ... + 46181.

It is an arithmetic number, because the mean of its divisors is an integer number (928620).

Almost surely, 2^18438381 is an apocalyptic number.

It is an amenable number.

18438381 is a deficient number, since it is larger than the sum of its proper divisors (11277459).

18438381 is a wasteful number, since it uses less digits than its factorization.

18438381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 554 (or 548 counting only the distinct ones).

The product of its digits is 18432, while the sum is 36.

The square root of 18438381 is about 4293.9935957102. The cubic root of 18438381 is about 264.1846590303.

The spelling of 18438381 in words is "eighteen million, four hundred thirty-eight thousand, three hundred eighty-one".