9911009981 has 2 divisors, whose sum is σ = 9911009982. Its totient is φ = 9911009980.

The previous prime is 9911009939. The next prime is 9911010029. The reversal of 9911009981 is 1899001199.

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., 7947722500 + 1963287481 = 89150^2 + 44309^2 .

It is a cyclic number.

It is not a de Polignac number, because 9911009981 - 2¹⁴ = 9910993597 is a prime.

It is a super-2 number, since 2×9911009981² (a number of 21 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 (9911009681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4955504990 + 4955504991.

It is an arithmetic number, because the mean of its divisors is an integer number (4955504991).

Almost surely, 2^9911009981 is an apocalyptic number.

It is an amenable number.

9911009981 is a deficient number, since it is larger than the sum of its proper divisors (1).

9911009981 is an equidigital number, since it uses as much as digits as its factorization.

9911009981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 52488, while the sum is 47.

The square root of 9911009981 is about 99554.0555728394. The cubic root of 9911009981 is about 2148.0248657836.

The spelling of 9911009981 in words is "nine billion, nine hundred eleven million, nine thousand, nine hundred eighty-one".