18399381 has 48 divisors (see below), whose sum is σ = 33247872. Its totient is φ = 8807040.

The previous prime is 18399377. The next prime is 18399413.

It is a happy number.

18399381 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 18399381 - 2² = 18399377 is a prime.

It is a super-2 number, since 2×18399381² = 677074442366322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18399361) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 32755 + ... + 33311.

It is an arithmetic number, because the mean of its divisors is an integer number (692664).

Almost surely, 2^18399381 is an apocalyptic number.

18399381 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

18399381 is a deficient number, since it is larger than the sum of its proper divisors (14848491).

18399381 is a wasteful number, since it uses less digits than its factorization.

18399381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 602 (or 591 counting only the distinct ones).

The product of its digits is 46656, while the sum is 42.

The square root of 18399381 is about 4289.4499647391. The cubic root of 18399381 is about 263.9982638775.

The spelling of 18399381 in words is "eighteen million, three hundred ninety-nine thousand, three hundred eighty-one".