19805 has 8 divisors (see below), whose sum is σ = 25272. Its totient is φ = 14848.

The previous prime is 19801. The next prime is 19813. The reversal of 19805 is 50891.

19805 is digitally balanced in base 6, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 1849 + 17956 = 43^2 + 134^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 19805 - 2² = 19801 is a prime.

It is an Ulam number.

It is a Duffinian number.

19805 is strictly pandigital in base 6.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19801) 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, 32 + ... + 201.

It is an arithmetic number, because the mean of its divisors is an integer number (3159).

2¹⁹⁸⁰⁵ is an apocalyptic number.

It is an amenable number.

19805 is a deficient number, since it is larger than the sum of its proper divisors (5467).

19805 is a wasteful number, since it uses less digits than its factorization.

19805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 255.

The product of its (nonzero) digits is 360, while the sum is 23.

The square root of 19805 is about 140.7302383996. The cubic root of 19805 is about 27.0556693199.

The spelling of 19805 in words is "nineteen thousand, eight hundred five".