19668391 has 2 divisors, whose sum is σ = 19668392. Its totient is φ = 19668390.

The previous prime is 19668359. The next prime is 19668403. The reversal of 19668391 is 19386691.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 19668391 - 2⁵ = 19668359 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19668191) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9834195 + 9834196.

It is an arithmetic number, because the mean of its divisors is an integer number (9834196).

Almost surely, 2^19668391 is an apocalyptic number.

19668391 is a deficient number, since it is larger than the sum of its proper divisors (1).

19668391 is an equidigital number, since it uses as much as digits as its factorization.

19668391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 69984, while the sum is 43.

The square root of 19668391 is about 4434.9059742006. The cubic root of 19668391 is about 269.9331841983.

The spelling of 19668391 in words is "nineteen million, six hundred sixty-eight thousand, three hundred ninety-one".