2021000011981 has 2 divisors, whose sum is σ = 2021000011982. Its totient is φ = 2021000011980.

The previous prime is 2021000011853. The next prime is 2021000012021. The reversal of 2021000011981 is 1891100001202.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1975404951081 + 45595060900 = 1405491^2 + 213530^2 .

It is a cyclic number.

It is not a de Polignac number, because 2021000011981 - 2⁷ = 2021000011853 is a prime.

It is a super-2 number, since 2×2021000011981² (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 (2021000012981) 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, 1010500005990 + 1010500005991.

It is an arithmetic number, because the mean of its divisors is an integer number (1010500005991).

Almost surely, 2^{2021000011981} is an apocalyptic number.

It is an amenable number.

2021000011981 is a deficient number, since it is larger than the sum of its proper divisors (1).

2021000011981 is an equidigital number, since it uses as much as digits as its factorization.

2021000011981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 288, while the sum is 25.

The spelling of 2021000011981 in words is "two trillion, twenty-one billion, eleven thousand, nine hundred eighty-one".