18405 has 12 divisors (see below), whose sum is σ = 31980. Its totient is φ = 9792.

The previous prime is 18401. The next prime is 18413. The reversal of 18405 is 50481.

It can be written as a sum of positive squares in 2 ways, for example, as 12321 + 6084 = 111^2 + 78^2 .

It is not a de Polignac number, because 18405 - 2² = 18401 is a prime.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18401) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 160 + ... + 249.

It is an arithmetic number, because the mean of its divisors is an integer number (2665).

2¹⁸⁴⁰⁵ is an apocalyptic number.

18405 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

18405 is a deficient number, since it is larger than the sum of its proper divisors (13575).

18405 is a wasteful number, since it uses less digits than its factorization.

18405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 420 (or 417 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 18.

The square root of 18405 is about 135.6650286551. The cubic root of 18405 is about 26.4025135348.

Adding to 18405 its reverse (50481), we get a palindrome (68886).

The spelling of 18405 in words is "eighteen thousand, four hundred five".