211231209991 has 2 divisors, whose sum is σ = 211231209992. Its totient is φ = 211231209990.

The previous prime is 211231209989. The next prime is 211231210039. The reversal of 211231209991 is 199902132112.

211231209991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 211231209991 - 2¹ = 211231209989 is a prime.

Together with 211231209989, 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 (211231209911) 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, 105615604995 + 105615604996.

It is an arithmetic number, because the mean of its divisors is an integer number (105615604996).

Almost surely, 2^211231209991 is an apocalyptic number.

211231209991 is a deficient number, since it is larger than the sum of its proper divisors (1).

211231209991 is an equidigital number, since it uses as much as digits as its factorization.

211231209991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 17496, while the sum is 40.

The spelling of 211231209991 in words is "two hundred eleven billion, two hundred thirty-one million, two hundred nine thousand, nine hundred ninety-one".