665535509 has 2 divisors, whose sum is σ = 665535510. Its totient is φ = 665535508.

The previous prime is 665535491. The next prime is 665535523. The reversal of 665535509 is 905535566.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 664505284 + 1030225 = 25778^2 + 1015^2 .

It is a cyclic number.

It is not a de Polignac number, because 665535509 - 2⁸ = 665535253 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 665535509.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665535569) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332767754 + 332767755.

It is an arithmetic number, because the mean of its divisors is an integer number (332767755).

Almost surely, 2^665535509 is an apocalyptic number.

It is an amenable number.

665535509 is a deficient number, since it is larger than the sum of its proper divisors (1).

665535509 is an equidigital number, since it uses as much as digits as its factorization.

665535509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 607500, while the sum is 44.

The square root of 665535509 is about 25797.9749011429. The cubic root of 665535509 is about 873.0861064121.

The spelling of 665535509 in words is "six hundred sixty-five million, five hundred thirty-five thousand, five hundred nine".