19440 has 60 divisors (see below), whose sum is σ = 67704. Its totient is φ = 5184.

The previous prime is 19433. The next prime is 19441. The reversal of 19440 is 4491.

It is a tau number, because it is divible by the number of its divisors (60).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a nialpdrome in base 3 and base 12.

It is a zygodrome in base 3.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19441) by changing a digit.

19440 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3886 + ... + 3890.

2¹⁹⁴⁴⁰ is an apocalyptic number.

19440 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 19440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33852).

19440 is an abundant number, since it is smaller than the sum of its proper divisors (48264).

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

19440 is an equidigital number, since it uses as much as digits as its factorization.

19440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28 (or 10 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 19440 is about 139.4274004635. The cubic root of 19440 is about 26.8884284793. Note that the first 3 decimals are identical.

The spelling of 19440 in words is "nineteen thousand, four hundred forty".