9991111181 has 2 divisors, whose sum is σ = 9991111182. Its totient is φ = 9991111180.

The previous prime is 9991111177. The next prime is 9991111187. The reversal of 9991111181 is 1811111999.

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., 7581184900 + 2409926281 = 87070^2 + 49091^2 .

It is an emirp because it is prime and its reverse (1811111999) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 9991111181 - 2² = 9991111177 is a prime.

It is a super-2 number, since 2×9991111181² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9991111187) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4995555590 + 4995555591.

It is an arithmetic number, because the mean of its divisors is an integer number (4995555591).

Almost surely, 2^9991111181 is an apocalyptic number.

It is an amenable number.

9991111181 is a deficient number, since it is larger than the sum of its proper divisors (1).

9991111181 is an equidigital number, since it uses as much as digits as its factorization.

9991111181 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5832, while the sum is 41.

The square root of 9991111181 is about 99955.5460242202. The cubic root of 9991111181 is about 2153.7961548001.

The spelling of 9991111181 in words is "nine billion, nine hundred ninety-one million, one hundred eleven thousand, one hundred eighty-one".