668781866 has 4 divisors (see below), whose sum is σ = 1003172802. Its totient is φ = 334390932.

The previous prime is 668781829. The next prime is 668781877. The reversal of 668781866 is 668187866.

It is a happy number.

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

It can be written as a sum of positive squares in only one way, i.e., 496621225 + 172160641 = 22285^2 + 13121^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 167195465 + ... + 167195468.

Almost surely, 2^668781866 is an apocalyptic number.

668781866 is a deficient number, since it is larger than the sum of its proper divisors (334390936).

668781866 is a wasteful number, since it uses less digits than its factorization.

668781866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 334390935.

The product of its digits is 4644864, while the sum is 56.

The square root of 668781866 is about 25860.8171951313. The cubic root of 668781866 is about 874.5033877487.

The spelling of 668781866 in words is "six hundred sixty-eight million, seven hundred eighty-one thousand, eight hundred sixty-six".