1211100019981 has 2 divisors, whose sum is σ = 1211100019982. Its totient is φ = 1211100019980.

The previous prime is 1211100019973. The next prime is 1211100020041. The reversal of 1211100019981 is 1899100011121.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 871142222500 + 339957797481 = 933350^2 + 583059^2 .

It is a cyclic number.

It is not a de Polignac number, because 1211100019981 - 2³ = 1211100019973 is a prime.

It is a super-2 number, since 2×1211100019981² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1211100019781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 605550009990 + 605550009991.

It is an arithmetic number, because the mean of its divisors is an integer number (605550009991).

Almost surely, 2^{1211100019981} is an apocalyptic number.

It is an amenable number.

1211100019981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1211100019981 is an equidigital number, since it uses as much as digits as its factorization.

1211100019981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1296, while the sum is 34.

The spelling of 1211100019981 in words is "one trillion, two hundred eleven billion, one hundred million, nineteen thousand, nine hundred eighty-one".