9991111231 has 2 divisors, whose sum is σ = 9991111232. Its totient is φ = 9991111230.

The previous prime is 9991111223. The next prime is 9991111279. The reversal of 9991111231 is 1321111999.

It is a weak prime.

It is an emirp because it is prime and its reverse (1321111999) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 9991111231 - 2³ = 9991111223 is a prime.

It is a super-2 number, since 2×9991111231² (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 (9991111331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4995555615 + 4995555616.

It is an arithmetic number, because the mean of its divisors is an integer number (4995555616).

Almost surely, 2^9991111231 is an apocalyptic number.

9991111231 is a deficient number, since it is larger than the sum of its proper divisors (1).

9991111231 is an equidigital number, since it uses as much as digits as its factorization.

9991111231 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4374, while the sum is 37.

The square root of 9991111231 is about 99955.5462743314. The cubic root of 9991111231 is about 2153.7961583930.

The spelling of 9991111231 in words is "nine billion, nine hundred ninety-one million, one hundred eleven thousand, two hundred thirty-one".