19840 has 32 divisors (see below), whose sum is σ = 48960. Its totient is φ = 7680.

The previous prime is 19819. The next prime is 19841. The reversal of 19840 is 4891.

19840 is digitally balanced in base 6, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (32).

19840 is strictly pandigital in base 6.

It is a nialpdrome in base 14.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19841) by changing a digit.

19840 is an untouchable number, because it is not equal to the sum of proper divisors of any 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, 625 + ... + 655.

It is an arithmetic number, because the mean of its divisors is an integer number (1530).

2¹⁹⁸⁴⁰ is an apocalyptic number.

19840 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 19840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24480).

19840 is an abundant number, since it is smaller than the sum of its proper divisors (29120).

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

19840 is an equidigital number, since it uses as much as digits as its factorization.

19840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50 (or 38 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 22.

The square root of 19840 is about 140.8545348933. The cubic root of 19840 is about 27.0715978084.

The spelling of 19840 in words is "nineteen thousand, eight hundred forty".