668705321 has 4 divisors (see below), whose sum is σ = 669520644. Its totient is φ = 667890000.

The previous prime is 668705291. The next prime is 668705333. The reversal of 668705321 is 123507866.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 349690000 + 319015321 = 18700^2 + 17861^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-668705321 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (668705221) 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, 406430 + ... + 408071.

It is an arithmetic number, because the mean of its divisors is an integer number (167380161).

Almost surely, 2^668705321 is an apocalyptic number.

It is an amenable number.

668705321 is a deficient number, since it is larger than the sum of its proper divisors (815323).

668705321 is an equidigital number, since it uses as much as digits as its factorization.

668705321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 815322.

The product of its (nonzero) digits is 60480, while the sum is 38.

The square root of 668705321 is about 25859.3372111506. The cubic root of 668705321 is about 874.4700229007.

The spelling of 668705321 in words is "six hundred sixty-eight million, seven hundred five thousand, three hundred twenty-one".