51565 has 4 divisors (see below), whose sum is σ = 61884. Its totient is φ = 41248.

The previous prime is 51563. The next prime is 51577. The reversal of 51565 is 56515.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 19881 + 31684 = 141^2 + 178^2 .

It is a cyclic number.

It is not a de Polignac number, because 51565 - 2¹ = 51563 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a plaindrome in base 8.

It is a nialpdrome in base 9.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51563) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5152 + ... + 5161.

It is an arithmetic number, because the mean of its divisors is an integer number (15471).

2⁵¹⁵⁶⁵ is an apocalyptic number.

It is an amenable number.

51565 is a deficient number, since it is larger than the sum of its proper divisors (10319).

51565 is a wasteful number, since it uses less digits than its factorization.

51565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10318.

The product of its digits is 750, while the sum is 22.

The square root of 51565 is about 227.0792813094. The cubic root of 51565 is about 37.2207403517.

Subtracting 51565 from its reverse (56515), we obtain a triangular number (4950 = T₉₉).

It can be divided in two parts, 51 and 565, that added together give a palindrome (616).

The spelling of 51565 in words is "fifty-one thousand, five hundred sixty-five".