18421381 has 8 divisors (see below), whose sum is σ = 20145024. Its totient is φ = 16705920.

The previous prime is 18421379. The next prime is 18421399. The reversal of 18421381 is 18312481.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 18421381 - 2¹ = 18421379 is a prime.

It is a super-2 number, since 2×18421381² = 678694555894322, 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 (18421681) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3285 + ... + 6901.

It is an arithmetic number, because the mean of its divisors is an integer number (2518128).

Almost surely, 2^18421381 is an apocalyptic number.

18421381 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

18421381 is a deficient number, since it is larger than the sum of its proper divisors (1723643).

18421381 is a wasteful number, since it uses less digits than its factorization.

18421381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4091.

The product of its digits is 1536, while the sum is 28.

The square root of 18421381 is about 4292.0136299877. The cubic root of 18421381 is about 264.1034422074.

Subtracting from 18421381 its reverse (18312481), we obtain a square (108900 = 330²).

It can be divided in two parts, 1842 and 1381, that added together give a palindrome (3223).

The spelling of 18421381 in words is "eighteen million, four hundred twenty-one thousand, three hundred eighty-one".