668616808616866 has 4 divisors (see below), whose sum is σ = 1002925212925302. Its totient is φ = 334308404308432.

The previous prime is 668616808616851. The next prime is 668616808616989.

668616808616866 is nontrivially palindromic in base 10.

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., 659999478107025 + 8617330509841 = 25690455^2 + 2935529^2 .

It is a super-2 number, since 2×668616808616866² (a number of 30 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 668616808616866.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 167154202154215 + ... + 167154202154218.

Almost surely, 2^{668616808616866} is an apocalyptic number.

668616808616866 is a deficient number, since it is larger than the sum of its proper divisors (334308404308436).

668616808616866 is a wasteful number, since it uses less digits than its factorization.

668616808616866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 334308404308435.

The product of its (nonzero) digits is 6879707136, while the sum is 82.

The spelling of 668616808616866 in words is "six hundred sixty-eight trillion, six hundred sixteen billion, eight hundred eight million, six hundred sixteen thousand, eight hundred sixty-six".