66809 has 2 divisors, whose sum is σ = 66810. Its totient is φ = 66808.

The previous prime is 66797. The next prime is 66821. The reversal of 66809 is 90866.

66809 is nontrivially palindromic in base 13.

It is a balanced prime because it is at equal distance from previous prime (66797) and next prime (66821).

It can be written as a sum of positive squares in only one way, i.e., 41209 + 25600 = 203^2 + 160^2 .

It is a cyclic number.

It is not a de Polignac number, because 66809 - 2⁸ = 66553 is a prime.

It is a Chen prime.

It is a plaindrome in base 15.

It is not a weakly prime, because it can be changed into another prime (66889) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33404 + 33405.

It is an arithmetic number, because the mean of its divisors is an integer number (33405).

2⁶⁶⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

66809 is a deficient number, since it is larger than the sum of its proper divisors (1).

66809 is an equidigital number, since it uses as much as digits as its factorization.

66809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2592, while the sum is 29.

The square root of 66809 is about 258.4743701027. The cubic root of 66809 is about 40.5768494613.

The spelling of 66809 in words is "sixty-six thousand, eight hundred nine".