66509 has 2 divisors, whose sum is σ = 66510. Its totient is φ = 66508.

The previous prime is 66499. The next prime is 66523. The reversal of 66509 is 90566.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 64009 + 2500 = 253^2 + 50^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66509 is a prime.

It is a Chen prime.

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 66509.

It is not a weakly prime, because it can be changed into another prime (66529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33254 + 33255.

It is an arithmetic number, because the mean of its divisors is an integer number (33255).

2⁶⁶⁵⁰⁹ is an apocalyptic number.

It is an amenable number.

66509 is a deficient number, since it is larger than the sum of its proper divisors (1).

66509 is an equidigital number, since it uses as much as digits as its factorization.

66509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1620, while the sum is 26.

The square root of 66509 is about 257.8933888257. The cubic root of 66509 is about 40.5160227208.

It can be divided in two parts, 66 and 509, that added together give a palindrome (575).

The spelling of 66509 in words is "sixty-six thousand, five hundred nine".