2021021111981 has 2 divisors, whose sum is σ = 2021021111982. Its totient is φ = 2021021111980.

The previous prime is 2021021111969. The next prime is 2021021112041. The reversal of 2021021111981 is 1891111201202.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1869317872900 + 151703239081 = 1367230^2 + 389491^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2021021111981 is a prime.

It is a super-2 number, since 2×2021021111981² (a number of 25 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2021021113981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1010510555990 + 1010510555991.

It is an arithmetic number, because the mean of its divisors is an integer number (1010510555991).

Almost surely, 2^{2021021111981} is an apocalyptic number.

It is an amenable number.

2021021111981 is a deficient number, since it is larger than the sum of its proper divisors (1).

2021021111981 is an equidigital number, since it uses as much as digits as its factorization.

2021021111981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 576, while the sum is 29.

The spelling of 2021021111981 in words is "two trillion, twenty-one billion, twenty-one million, one hundred eleven thousand, nine hundred eighty-one".