66565 has 4 divisors (see below), whose sum is σ = 79884. Its totient is φ = 53248.

The previous prime is 66553. The next prime is 66569. The reversal of 66565 is 56566.

It is a Cunningham number, because it is equal to 258²+1.

66565 is an esthetic number in base 6, because in such base its adjacent digits differ by 1.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 56566 = 2 ⋅28283.

It can be written as a sum of positive squares in 2 ways, for example, as 23716 + 42849 = 154^2 + 207^2 .

It is a cyclic number.

It is not a de Polignac number, because 66565 - 2⁵ = 66533 is a prime.

It is a Duffinian number.

66565 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66569) 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, 6652 + ... + 6661.

It is an arithmetic number, because the mean of its divisors is an integer number (19971).

2⁶⁶⁵⁶⁵ is an apocalyptic number.

It is an amenable number.

66565 is a deficient number, since it is larger than the sum of its proper divisors (13319).

66565 is a wasteful number, since it uses less digits than its factorization.

66565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13318.

The product of its digits is 5400, while the sum is 28.

The square root of 66565 is about 258.0019379772. The cubic root of 66565 is about 40.5273909105.

Subtracting from 66565 its reverse (56566), we obtain a palindrome (9999).

The spelling of 66565 in words is "sixty-six thousand, five hundred sixty-five".