1805 has 6 divisors (see below), whose sum is σ = 2286. Its totient is φ = 1368.

The previous prime is 1801. The next prime is 1811. The reversal of 1805 is 5081.

1805 is nontrivially palindromic in base 4.

It can be written as a sum of positive squares in only one way, i.e., 1444 + 361 = 38^2 + 19^2 .

It is not a de Polignac number, because 1805 - 2² = 1801 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1805.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1801) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 86 + ... + 104.

It is an arithmetic number, because the mean of its divisors is an integer number (381).

2¹⁸⁰⁵ is an apocalyptic number.

It is an amenable number.

1805 is a deficient number, since it is larger than the sum of its proper divisors (481).

1805 is an equidigital number, since it uses as much as digits as its factorization.

1805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43 (or 24 counting only the distinct ones).

The product of its (nonzero) digits is 40, while the sum is 14.

The square root of 1805 is about 42.4852915725. The cubic root of 1805 is about 12.1756569152.

Adding to 1805 its reverse (5081), we get a palindrome (6886).

It can be divided in two parts, 180 and 5, that multiplied together give a square (900 = 30²).

The spelling of 1805 in words is "one thousand, eight hundred five".