21108306391 has 2 divisors, whose sum is σ = 21108306392. Its totient is φ = 21108306390.

The previous prime is 21108306389. The next prime is 21108306467. The reversal of 21108306391 is 19360380112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21108306391 - 2¹ = 21108306389 is a prime.

Together with 21108306389, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21108306301) 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, 10554153195 + 10554153196.

It is an arithmetic number, because the mean of its divisors is an integer number (10554153196).

Almost surely, 2^21108306391 is an apocalyptic number.

21108306391 is a deficient number, since it is larger than the sum of its proper divisors (1).

21108306391 is an equidigital number, since it uses as much as digits as its factorization.

21108306391 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7776, while the sum is 34.

The spelling of 21108306391 in words is "twenty-one billion, one hundred eight million, three hundred six thousand, three hundred ninety-one".