18640 has 20 divisors (see below), whose sum is σ = 43524. Its totient is φ = 7424.

The previous prime is 18637. The next prime is 18661. The reversal of 18640 is 4681.

It can be written as a sum of positive squares in 2 ways, for example, as 5184 + 13456 = 72^2 + 116^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is an Ulam number.

It is a nialpdrome in base 8 and base 12.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 37 + ... + 196.

2¹⁸⁶⁴⁰ is an apocalyptic number.

18640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

18640 is an abundant number, since it is smaller than the sum of its proper divisors (24884).

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 (21762).

18640 is a wasteful number, since it uses less digits than its factorization.

18640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 246 (or 240 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 19.

The square root of 18640 is about 136.5283853270. The cubic root of 18640 is about 26.5144101050.

The spelling of 18640 in words is "eighteen thousand, six hundred forty".