665396209 has 2 divisors, whose sum is σ = 665396210. Its totient is φ = 665396208.

The previous prime is 665396203. The next prime is 665396239. The reversal of 665396209 is 902693566.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 664866225 + 529984 = 25785^2 + 728^2 .

It is a cyclic number.

It is not a de Polignac number, because 665396209 - 2⁵ = 665396177 is a prime.

It is a super-2 number, since 2×665396209² = 885504229903143362, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (665396203) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332698104 + 332698105.

It is an arithmetic number, because the mean of its divisors is an integer number (332698105).

Almost surely, 2^665396209 is an apocalyptic number.

It is an amenable number.

665396209 is a deficient number, since it is larger than the sum of its proper divisors (1).

665396209 is an equidigital number, since it uses as much as digits as its factorization.

665396209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 524880, while the sum is 46.

The square root of 665396209 is about 25795.2749355381. The cubic root of 665396209 is about 873.0251883598.

The spelling of 665396209 in words is "six hundred sixty-five million, three hundred ninety-six thousand, two hundred nine".