51805 has 8 divisors (see below), whose sum is σ = 67032. Its totient is φ = 38208.

The previous prime is 51803. The next prime is 51817. The reversal of 51805 is 50815.

It can be written as a sum of positive squares in 4 ways, for example, as 729 + 51076 = 27^2 + 226^2 .

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 51805 - 2¹ = 51803 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51803) 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, 334 + ... + 463.

It is an arithmetic number, because the mean of its divisors is an integer number (8379).

2⁵¹⁸⁰⁵ is an apocalyptic number.

It is an amenable number.

51805 is a deficient number, since it is larger than the sum of its proper divisors (15227).

51805 is a wasteful number, since it uses less digits than its factorization.

51805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 815.

The product of its (nonzero) digits is 200, while the sum is 19.

The square root of 51805 is about 227.6071176391. The cubic root of 51805 is about 37.2783967364.

Subtracting from 51805 its reverse (50815), we obtain a triangular number (990 = T₄₄).

It can be divided in two parts, 5 and 1805, that multiplied together give a square (9025 = 95²).

The spelling of 51805 in words is "fifty-one thousand, eight hundred five".