668619209 has 4 divisors (see below), whose sum is σ = 668678400. Its totient is φ = 668560020.

The previous prime is 668619179. The next prime is 668619229. The reversal of 668619209 is 902916866.

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, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 902916866 = 2 ⋅451458433.

It is a cyclic number.

It is not a de Polignac number, because 668619209 - 2⁸ = 668618953 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (668619229) 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, 6797 + ... + 37194.

It is an arithmetic number, because the mean of its divisors is an integer number (167169600).

Almost surely, 2^668619209 is an apocalyptic number.

It is an amenable number.

668619209 is a deficient number, since it is larger than the sum of its proper divisors (59191).

668619209 is a wasteful number, since it uses less digits than its factorization.

668619209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59190.

The product of its (nonzero) digits is 279936, while the sum is 47.

The square root of 668619209 is about 25857.6721496735. The cubic root of 668619209 is about 874.4324848937.

The spelling of 668619209 in words is "six hundred sixty-eight million, six hundred nineteen thousand, two hundred nine".