668888861 has 2 divisors, whose sum is σ = 668888862. Its totient is φ = 668888860.

The previous prime is 668888833. The next prime is 668888867. The reversal of 668888861 is 168888866.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 651831961 + 17056900 = 25531^2 + 4130^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-668888861 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 668888861.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (668888867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334444430 + 334444431.

It is an arithmetic number, because the mean of its divisors is an integer number (334444431).

Almost surely, 2^668888861 is an apocalyptic number.

It is an amenable number.

668888861 is a deficient number, since it is larger than the sum of its proper divisors (1).

668888861 is an equidigital number, since it uses as much as digits as its factorization.

668888861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7077888, while the sum is 59.

The square root of 668888861 is about 25862.8857825263. The cubic root of 668888861 is about 874.5500210409.

The spelling of 668888861 in words is "six hundred sixty-eight million, eight hundred eighty-eight thousand, eight hundred sixty-one".