51806 has 4 divisors (see below), whose sum is σ = 77712. Its totient is φ = 25902.

The previous prime is 51803. The next prime is 51817. The reversal of 51806 is 60815.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 60815 = 5 ⋅12163.

It is a Curzon number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 51806.

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 as a sum of consecutive naturals, namely, 12950 + ... + 12953.

It is an arithmetic number, because the mean of its divisors is an integer number (19428).

2⁵¹⁸⁰⁶ is an apocalyptic number.

51806 is a deficient number, since it is larger than the sum of its proper divisors (25906).

51806 is a wasteful number, since it uses less digits than its factorization.

51806 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25905.

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

The square root of 51806 is about 227.6093143964. The cubic root of 51806 is about 37.2786365984.

Subtracting 51806 from its reverse (60815), we obtain a palindrome (9009).

The spelling of 51806 in words is "fifty-one thousand, eight hundred six".