18388381 has 4 divisors (see below), whose sum is σ = 20060064. Its totient is φ = 16716700.

The previous prime is 18388369. The next prime is 18388411.

18388381 is nontrivially palindromic in base 10.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 18388381 - 2¹³ = 18380189 is a prime.

It is a super-2 number, since 2×18388381² = 676265111602322, 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 (18388681) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 835825 + ... + 835846.

It is an arithmetic number, because the mean of its divisors is an integer number (5015016).

Almost surely, 2^18388381 is an apocalyptic number.

18388381 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

18388381 is a deficient number, since it is larger than the sum of its proper divisors (1671683).

18388381 is a wasteful number, since it uses less digits than its factorization.

18388381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1671682.

The product of its digits is 36864, while the sum is 40.

The square root of 18388381 is about 4288.1675573606. The cubic root of 18388381 is about 263.9456432702.

It can be divided in two parts, 18388 and 381, that added together give a square (18769 = 137²).

The spelling of 18388381 in words is "eighteen million, three hundred eighty-eight thousand, three hundred eighty-one".