991100991 has 8 divisors (see below), whose sum is σ = 1321802800. Its totient is φ = 660566592.

The previous prime is 991100987. The next prime is 991101017. The reversal of 991100991 is 199001199.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 991100991 - 2² = 991100987 is a prime.

It is a super-2 number, since 2×991100991² = 1964562348722364162, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991100941) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 27316 + ... + 52233.

It is an arithmetic number, because the mean of its divisors is an integer number (165225350).

Almost surely, 2^991100991 is an apocalyptic number.

991100991 is a deficient number, since it is larger than the sum of its proper divisors (330701809).

991100991 is a wasteful number, since it uses less digits than its factorization.

991100991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83705.

The product of its (nonzero) digits is 6561, while the sum is 39.

The square root of 991100991 is about 31481.7564789514. The cubic root of 991100991 is about 997.0248207536.

The spelling of 991100991 in words is "nine hundred ninety-one million, one hundred thousand, nine hundred ninety-one".