668509 has 2 divisors, whose sum is σ = 668510. Its totient is φ = 668508.

The previous prime is 668471. The next prime is 668513. The reversal of 668509 is 905866.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 525625 + 142884 = 725^2 + 378^2 .

It is a cyclic number.

It is not a de Polignac number, because 668509 - 2¹¹ = 666461 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (668539) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334254 + 334255.

It is an arithmetic number, because the mean of its divisors is an integer number (334255).

2⁶⁶⁸⁵⁰⁹ is an apocalyptic number.

It is an amenable number.

668509 is a deficient number, since it is larger than the sum of its proper divisors (1).

668509 is an equidigital number, since it uses as much as digits as its factorization.

668509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 668509 is about 817.6239967124. The cubic root of 668509 is about 87.4384437802.

The spelling of 668509 in words is "six hundred sixty-eight thousand, five hundred nine".