665970209 has 2 divisors, whose sum is σ = 665970210. Its totient is φ = 665970208.

The previous prime is 665970203. The next prime is 665970211. The reversal of 665970209 is 902079566.

665970209 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 549761809 + 116208400 = 23447^2 + 10780^2 .

It is a cyclic number.

It is not a de Polignac number, because 665970209 - 2¹² = 665966113 is a prime.

Together with 665970211, it forms a pair of twin primes.

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 665970209.

It is not a weakly prime, because it can be changed into another prime (665970203) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332985104 + 332985105.

It is an arithmetic number, because the mean of its divisors is an integer number (332985105).

Almost surely, 2^665970209 is an apocalyptic number.

It is an amenable number.

665970209 is a deficient number, since it is larger than the sum of its proper divisors (1).

665970209 is an equidigital number, since it uses as much as digits as its factorization.

665970209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 204120, while the sum is 44.

The square root of 665970209 is about 25806.3986057722. The cubic root of 665970209 is about 873.2761528354.

The spelling of 665970209 in words is "six hundred sixty-five million, nine hundred seventy thousand, two hundred nine".