660809 has 2 divisors, whose sum is σ = 660810. Its totient is φ = 660808.

The previous prime is 660799. The next prime is 660811. The reversal of 660809 is 908066.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 635209 + 25600 = 797^2 + 160^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-660809 is a prime.

Together with 660811, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (660899) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330404 + 330405.

It is an arithmetic number, because the mean of its divisors is an integer number (330405).

2⁶⁶⁰⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

660809 is a deficient number, since it is larger than the sum of its proper divisors (1).

660809 is an equidigital number, since it uses as much as digits as its factorization.

660809 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 660809 is about 812.9015930603. The cubic root of 660809 is about 87.1014362727.

The spelling of 660809 in words is "six hundred sixty thousand, eight hundred nine".