1211011111991 has 2 divisors, whose sum is σ = 1211011111992. Its totient is φ = 1211011111990.

The previous prime is 1211011111967. The next prime is 1211011112023. The reversal of 1211011111991 is 1991111101121.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1211011111991 - 2³⁰ = 1209937370167 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1211011111931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 605505555995 + 605505555996.

It is an arithmetic number, because the mean of its divisors is an integer number (605505555996).

Almost surely, 2^{1211011111991} is an apocalyptic number.

1211011111991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1211011111991 is an equidigital number, since it uses as much as digits as its factorization.

1211011111991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 162, while the sum is 29.

The spelling of 1211011111991 in words is "one trillion, two hundred eleven billion, eleven million, one hundred eleven thousand, nine hundred ninety-one".