19818 has 16 divisors (see below), whose sum is σ = 44160. Its totient is φ = 6588.

The previous prime is 19813. The next prime is 19819. The reversal of 19818 is 81891.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a junction number, because it is equal to n+sod(n) for n = 19791 and 19800.

It is not an unprimeable number, because it can be changed into a prime (19813) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 130 + ... + 237.

It is an arithmetic number, because the mean of its divisors is an integer number (2760).

2¹⁹⁸¹⁸ is an apocalyptic number.

19818 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

19818 is an abundant number, since it is smaller than the sum of its proper divisors (24342).

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 (22080).

19818 is a wasteful number, since it uses less digits than its factorization.

19818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 378 (or 372 counting only the distinct ones).

The product of its digits is 576, while the sum is 27.

The square root of 19818 is about 140.7764184798. The cubic root of 19818 is about 27.0615878046.

Subtracting from 19818 its sum of digits (27), we obtain a palindrome (19791).

It can be divided in two parts, 198 and 18, that added together give a cube (216 = 6³).

The spelling of 19818 in words is "nineteen thousand, eight hundred eighteen".