18720 has 72 divisors (see below), whose sum is σ = 68796. Its totient is φ = 4608.

The previous prime is 18719. The next prime is 18731. The reversal of 18720 is 2781.

It can be written as a sum of positive squares in 2 ways, for example, as 17424 + 1296 = 132^2 + 36^2 .

It is a tau number, because it is divible by the number of its divisors (72).

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

It is a nialpdrome in base 8 and base 12.

It is a zygodrome in base 12.

It is a junction number, because it is equal to n+sod(n) for n = 18693 and 18702.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 18720.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1434 + ... + 1446.

2¹⁸⁷²⁰ is an apocalyptic number.

18720 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 18720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34398).

18720 is an abundant number, since it is smaller than the sum of its proper divisors (50076).

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

18720 is a wasteful number, since it uses less digits than its factorization.

18720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34 (or 23 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 18.

The square root of 18720 is about 136.8210510119. The cubic root of 18720 is about 26.5522878852.

The spelling of 18720 in words is "eighteen thousand, seven hundred twenty".