668501861 has 2 divisors, whose sum is σ = 668501862. Its totient is φ = 668501860.

The previous prime is 668501857. The next prime is 668501891. The reversal of 668501861 is 168105866.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 539679361 + 128822500 = 23231^2 + 11350^2 .

It is a cyclic number.

It is not a de Polignac number, because 668501861 - 2² = 668501857 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (668501891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334250930 + 334250931.

It is an arithmetic number, because the mean of its divisors is an integer number (334250931).

Almost surely, 2^668501861 is an apocalyptic number.

It is an amenable number.

668501861 is a deficient number, since it is larger than the sum of its proper divisors (1).

668501861 is an equidigital number, since it uses as much as digits as its factorization.

668501861 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 69120, while the sum is 41.

The square root of 668501861 is about 25855.4029363303. The cubic root of 668501861 is about 874.3813252772.

The spelling of 668501861 in words is "six hundred sixty-eight million, five hundred one thousand, eight hundred sixty-one".