211111999981 has 2 divisors, whose sum is σ = 211111999982. Its totient is φ = 211111999980.

The previous prime is 211111999979. The next prime is 211111999993. The reversal of 211111999981 is 189999111112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 197232803881 + 13879196100 = 444109^2 + 117810^2 .

It is a cyclic number.

It is not a de Polignac number, because 211111999981 - 2¹ = 211111999979 is a prime.

It is a super-2 number, since 2×211111999981² (a number of 23 digits) contains 22 as substring.

Together with 211111999979, 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 (211111999781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 105555999990 + 105555999991.

It is an arithmetic number, because the mean of its divisors is an integer number (105555999991).

Almost surely, 2^211111999981 is an apocalyptic number.

It is an amenable number.

211111999981 is a deficient number, since it is larger than the sum of its proper divisors (1).

211111999981 is an equidigital number, since it uses as much as digits as its factorization.

211111999981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 104976, while the sum is 52.

The spelling of 211111999981 in words is "two hundred eleven billion, one hundred eleven million, nine hundred ninety-nine thousand, nine hundred eighty-one".