668509217 has 4 divisors (see below), whose sum is σ = 670331136. Its totient is φ = 666687300.

The previous prime is 668509199. The next prime is 668509267. The reversal of 668509217 is 712905866.

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 668509217 - 2¹² = 668505121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (668509267) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 910409 + ... + 911142.

It is an arithmetic number, because the mean of its divisors is an integer number (167582784).

Almost surely, 2^668509217 is an apocalyptic number.

It is an amenable number.

668509217 is a deficient number, since it is larger than the sum of its proper divisors (1821919).

668509217 is a wasteful number, since it uses less digits than its factorization.

668509217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1821918.

The product of its (nonzero) digits is 181440, while the sum is 44.

The square root of 668509217 is about 25855.5451886051. The cubic root of 668509217 is about 874.3845324113.

It can be divided in two parts, 66850 and 9217, that added together give a palindrome (76067).

The spelling of 668509217 in words is "six hundred sixty-eight million, five hundred nine thousand, two hundred seventeen".