18391833821 has 2 divisors, whose sum is σ = 18391833822. Its totient is φ = 18391833820.

The previous prime is 18391833799. The next prime is 18391833839. The reversal of 18391833821 is 12833819381.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17679691225 + 712142596 = 132965^2 + 26686^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18391833821 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18391833851) 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, 9195916910 + 9195916911.

It is an arithmetic number, because the mean of its divisors is an integer number (9195916911).

Almost surely, 2^18391833821 is an apocalyptic number.

It is an amenable number.

18391833821 is a deficient number, since it is larger than the sum of its proper divisors (1).

18391833821 is an equidigital number, since it uses as much as digits as its factorization.

18391833821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 248832, while the sum is 47.

The spelling of 18391833821 in words is "eighteen billion, three hundred ninety-one million, eight hundred thirty-three thousand, eight hundred twenty-one".