665212409 has 4 divisors (see below), whose sum is σ = 666546000. Its totient is φ = 663878820.

The previous prime is 665212369. The next prime is 665212447. The reversal of 665212409 is 904212566.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 665212409 - 2²⁰ = 664163833 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (665212489) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 666047 + ... + 667044.

It is an arithmetic number, because the mean of its divisors is an integer number (166636500).

Almost surely, 2^665212409 is an apocalyptic number.

It is an amenable number.

665212409 is a deficient number, since it is larger than the sum of its proper divisors (1333591).

665212409 is a wasteful number, since it uses less digits than its factorization.

665212409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1333590.

The product of its (nonzero) digits is 25920, while the sum is 35.

The square root of 665212409 is about 25791.7120215002. The cubic root of 665212409 is about 872.9447967553.

The spelling of 665212409 in words is "six hundred sixty-five million, two hundred twelve thousand, four hundred nine".