16805 has 4 divisors (see below), whose sum is σ = 20172. Its totient is φ = 13440.

The previous prime is 16787. The next prime is 16811. The reversal of 16805 is 50861.

16805 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 50861 = 181 ⋅281.

It can be written as a sum of positive squares in 2 ways, for example, as 9409 + 7396 = 97^2 + 86^2 .

It is not a de Polignac number, because 16805 - 2⁶ = 16741 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 7 and base 12.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1676 + ... + 1685.

It is an arithmetic number, because the mean of its divisors is an integer number (5043).

2¹⁶⁸⁰⁵ is an apocalyptic number.

It is an amenable number.

16805 is a deficient number, since it is larger than the sum of its proper divisors (3367).

16805 is an equidigital number, since it uses as much as digits as its factorization.

16805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3366.

The product of its (nonzero) digits is 240, while the sum is 20.

The square root of 16805 is about 129.6341004520. The cubic root of 16805 is about 25.6141238794.

It can be divided in two parts, 16 and 805, that multiplied together give a triangular number (12880 = T₁₆₀).

The spelling of 16805 in words is "sixteen thousand, eight hundred five".