65509 has 4 divisors (see below), whose sum is σ = 66220. Its totient is φ = 64800.

The previous prime is 65497. The next prime is 65519. The reversal of 65509 is 90556.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 50625 + 14884 = 225^2 + 122^2 .

It is a cyclic number.

It is not a de Polignac number, because 65509 - 2⁷ = 65381 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 4 and base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (65519) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 192 + ... + 409.

It is an arithmetic number, because the mean of its divisors is an integer number (16555).

2⁶⁵⁵⁰⁹ is an apocalyptic number.

It is an amenable number.

65509 is a deficient number, since it is larger than the sum of its proper divisors (711).

65509 is a wasteful number, since it uses less digits than its factorization.

65509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 710.

The product of its (nonzero) digits is 1350, while the sum is 25.

The square root of 65509 is about 255.9472601924. The cubic root of 65509 is about 40.3119360737.

The spelling of 65509 in words is "sixty-five thousand, five hundred nine".