18438431 has 4 divisors (see below), whose sum is σ = 20114664. Its totient is φ = 16762200.

The previous prime is 18438391. The next prime is 18438437. The reversal of 18438431 is 13483481.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 18438431 - 2¹⁰ = 18437407 is a prime.

It is a super-2 number, since 2×18438431² = 679951475483522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18438437) 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 3 ways as a sum of consecutive naturals, for example, 838100 + ... + 838121.

It is an arithmetic number, because the mean of its divisors is an integer number (5028666).

Almost surely, 2^18438431 is an apocalyptic number.

18438431 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

18438431 is a deficient number, since it is larger than the sum of its proper divisors (1676233).

18438431 is a wasteful number, since it uses less digits than its factorization.

18438431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1676232.

The product of its digits is 9216, while the sum is 32.

The square root of 18438431 is about 4293.9994177922. Note that the first 3 decimals coincide. The cubic root of 18438431 is about 264.1848978297.

The spelling of 18438431 in words is "eighteen million, four hundred thirty-eight thousand, four hundred thirty-one".