1668439391 has 2 divisors, whose sum is σ = 1668439392. Its totient is φ = 1668439390.

The previous prime is 1668439351. The next prime is 1668439441. The reversal of 1668439391 is 1939348661.

It is an a-pointer prime, because the next prime (1668439441) can be obtained adding 1668439391 to its sum of digits (50).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1668439391 - 2⁶ = 1668439327 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1668439351) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 834219695 + 834219696.

It is an arithmetic number, because the mean of its divisors is an integer number (834219696).

Almost surely, 2^1668439391 is an apocalyptic number.

1668439391 is a deficient number, since it is larger than the sum of its proper divisors (1).

1668439391 is an equidigital number, since it uses as much as digits as its factorization.

1668439391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 839808, while the sum is 50.

The square root of 1668439391 is about 40846.5346265751. The cubic root of 1668439391 is about 1186.0513119692.

The spelling of 1668439391 in words is "one billion, six hundred sixty-eight million, four hundred thirty-nine thousand, three hundred ninety-one".