1211021101991 has 2 divisors, whose sum is σ = 1211021101992. Its totient is φ = 1211021101990.

The previous prime is 1211021101957. The next prime is 1211021102099. The reversal of 1211021101991 is 1991011201121.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1211021101991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1211021101931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 605510550995 + 605510550996.

It is an arithmetic number, because the mean of its divisors is an integer number (605510550996).

Almost surely, 2^{1211021101991} is an apocalyptic number.

1211021101991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1211021101991 is an equidigital number, since it uses as much as digits as its factorization.

1211021101991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 324, while the sum is 29.

The spelling of 1211021101991 in words is "one trillion, two hundred eleven billion, twenty-one million, one hundred one thousand, nine hundred ninety-one".