18440 has 16 divisors (see below), whose sum is σ = 41580. Its totient is φ = 7360.

The previous prime is 18439. The next prime is 18443. The reversal of 18440 is 4481.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 17956 + 484 = 134^2 + 22^2 .

It is not an unprimeable number, because it can be changed into a prime (18443) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (3) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 191 + ... + 270.

2¹⁸⁴⁴⁰ is an apocalyptic number.

18440 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

18440 is an abundant number, since it is smaller than the sum of its proper divisors (23140).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (20790).

18440 is a wasteful number, since it uses less digits than its factorization.

18440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 472 (or 468 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 17.

The square root of 18440 is about 135.7939615741. The cubic root of 18440 is about 26.4192391134.

The spelling of 18440 in words is "eighteen thousand, four hundred forty".