19845 has 30 divisors (see below), whose sum is σ = 41382. Its totient is φ = 9072.

The previous prime is 19843. The next prime is 19853. The reversal of 19845 is 54891.

19845 is nontrivially palindromic in base 14.

It can be written as a sum of positive squares in only one way, i.e., 15876 + 3969 = 126^2 + 63^2 .

It is not a de Polignac number, because 19845 - 2¹ = 19843 is a prime.

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

Its product of digits (1440) is a multiple of the sum of its prime divisors (15).

It is a congruent number.

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

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 2832 + ... + 2838.

19845 is a Friedman number, since it can be written as 81*49*5, using all its digits and the basic arithmetic operations.

2¹⁹⁸⁴⁵ is an apocalyptic number.

19845 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

19845 is an abundant number, since it is smaller than the sum of its proper divisors (21537).

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 (20691).

19845 is an equidigital number, since it uses as much as digits as its factorization.

19845 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31 (or 15 counting only the distinct ones).

The product of its digits is 1440, while the sum is 27.

The square root of 19845 is about 140.8722825825. The cubic root of 19845 is about 27.0738717772.

It can be divided in two parts, 198 and 45, that added together give a 5-th power (243 = 3⁵).

The spelling of 19845 in words is "nineteen thousand, eight hundred forty-five".