668878817 has 2 divisors, whose sum is σ = 668878818. Its totient is φ = 668878816.

The previous prime is 668878789. The next prime is 668878841. The reversal of 668878817 is 718878866.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 614841616 + 54037201 = 24796^2 + 7351^2 .

It is a cyclic number.

It is not a de Polignac number, because 668878817 - 2²⁸ = 400443361 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (668878867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334439408 + 334439409.

It is an arithmetic number, because the mean of its divisors is an integer number (334439409).

Almost surely, 2^668878817 is an apocalyptic number.

It is an amenable number.

668878817 is a deficient number, since it is larger than the sum of its proper divisors (1).

668878817 is an equidigital number, since it uses as much as digits as its factorization.

668878817 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7225344, while the sum is 59.

The square root of 668878817 is about 25862.6916039302. The cubic root of 668878817 is about 874.5456436199.

The spelling of 668878817 in words is "six hundred sixty-eight million, eight hundred seventy-eight thousand, eight hundred seventeen".