668311657 has 4 divisors (see below), whose sum is σ = 719720260. Its totient is φ = 616903056.

The previous prime is 668311613. The next prime is 668311673. The reversal of 668311657 is 756113866.

668311657 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 756113866 = 2 ⋅378056933.

It can be written as a sum of positive squares in 2 ways, for example, as 384591321 + 283720336 = 19611^2 + 16844^2 .

It is a cyclic number.

It is not a de Polignac number, because 668311657 - 2¹⁵ = 668278889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (668311687) 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, 25704282 + ... + 25704307.

It is an arithmetic number, because the mean of its divisors is an integer number (179930065).

Almost surely, 2^668311657 is an apocalyptic number.

It is an amenable number.

668311657 is a deficient number, since it is larger than the sum of its proper divisors (51408603).

668311657 is a wasteful number, since it uses less digits than its factorization.

668311657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51408602.

The product of its digits is 181440, while the sum is 43.

The square root of 668311657 is about 25851.7244492510. The cubic root of 668311657 is about 874.2983902793.

The spelling of 668311657 in words is "six hundred sixty-eight million, three hundred eleven thousand, six hundred fifty-seven".