9811981 has 2 divisors, whose sum is σ = 9811982. Its totient is φ = 9811980.

The previous prime is 9811973. The next prime is 9812017. The reversal of 9811981 is 1891189.

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., 5103081 + 4708900 = 2259^2 + 2170^2 .

It is an emirp because it is prime and its reverse (1891189) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 9811981 - 2³ = 9811973 is a prime.

It is a super-2 number, since 2×9811981² = 192549942288722, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 9811981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9811381) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4905990 + 4905991.

It is an arithmetic number, because the mean of its divisors is an integer number (4905991).

Almost surely, 2^9811981 is an apocalyptic number.

It is an amenable number.

9811981 is a deficient number, since it is larger than the sum of its proper divisors (1).

9811981 is an equidigital number, since it uses as much as digits as its factorization.

9811981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5184, while the sum is 37.

The square root of 9811981 is about 3132.4081790214. The cubic root of 9811981 is about 214.0846682176.

The spelling of 9811981 in words is "nine million, eight hundred eleven thousand, nine hundred eighty-one".