1668666401 has 2 divisors, whose sum is σ = 1668666402. Its totient is φ = 1668666400.

The previous prime is 1668666359. The next prime is 1668666403. The reversal of 1668666401 is 1046668661.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1668640801 + 25600 = 40849^2 + 160^2 .

It is an emirp because it is prime and its reverse (1046668661) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1668666401 is a prime.

Together with 1668666403, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (1668666403) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 834333200 + 834333201.

It is an arithmetic number, because the mean of its divisors is an integer number (834333201).

Almost surely, 2^1668666401 is an apocalyptic number.

It is an amenable number.

1668666401 is a deficient number, since it is larger than the sum of its proper divisors (1).

1668666401 is an equidigital number, since it uses as much as digits as its factorization.

1668666401 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 248832, while the sum is 44.

The square root of 1668666401 is about 40849.3133479622. The cubic root of 1668666401 is about 1186.1051014165.

The spelling of 1668666401 in words is "one billion, six hundred sixty-eight million, six hundred sixty-six thousand, four hundred one".