19993421891 has 2 divisors, whose sum is σ = 19993421892. Its totient is φ = 19993421890.

The previous prime is 19993421887. The next prime is 19993421893. The reversal of 19993421891 is 19812439991.

It is a strong prime.

It is an emirp because it is prime and its reverse (19812439991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19993421891 - 2² = 19993421887 is a prime.

It is a Sophie Germain prime.

Together with 19993421893, 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 (19993421893) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9996710945 + 9996710946.

It is an arithmetic number, because the mean of its divisors is an integer number (9996710946).

Almost surely, 2^19993421891 is an apocalyptic number.

19993421891 is a deficient number, since it is larger than the sum of its proper divisors (1).

19993421891 is an equidigital number, since it uses as much as digits as its factorization.

19993421891 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1259712, while the sum is 56.

The spelling of 19993421891 in words is "nineteen billion, nine hundred ninety-three million, four hundred twenty-one thousand, eight hundred ninety-one".