2021011981 has 2 divisors, whose sum is σ = 2021011982. Its totient is φ = 2021011980.

The previous prime is 2021011973. The next prime is 2021012009. The reversal of 2021011981 is 1891101202.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1371220900 + 649791081 = 37030^2 + 25491^2 .

It is a cyclic number.

It is not a de Polignac number, because 2021011981 - 2³ = 2021011973 is a prime.

It is a super-2 number, since 2×2021011981² = 8168978854691088722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2021014981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1010505990 + 1010505991.

It is an arithmetic number, because the mean of its divisors is an integer number (1010505991).

Almost surely, 2^2021011981 is an apocalyptic number.

It is an amenable number.

2021011981 is a deficient number, since it is larger than the sum of its proper divisors (1).

2021011981 is an equidigital number, since it uses as much as digits as its factorization.

2021011981 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 square root of 2021011981 is about 44955.6668396766. Note that the first 3 decimals coincide. The cubic root of 2021011981 is about 1264.3179273322.

The spelling of 2021011981 in words is "two billion, twenty-one million, eleven thousand, nine hundred eighty-one".