991191975 has 12 divisors (see below), whose sum is σ = 1638770856. Its totient is φ = 528635680.

The previous prime is 991191941. The next prime is 991191979. The reversal of 991191975 is 579191199.

It is not a de Polignac number, because 991191975 - 2⁶ = 991191911 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991191979) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6607872 + ... + 6608021.

It is an arithmetic number, because the mean of its divisors is an integer number (136564238).

Almost surely, 2^991191975 is an apocalyptic number.

991191975 is a deficient number, since it is larger than the sum of its proper divisors (647578881).

991191975 is a wasteful number, since it uses less digits than its factorization.

991191975 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13215906 (or 13215901 counting only the distinct ones).

The product of its digits is 229635, while the sum is 51.

The square root of 991191975 is about 31483.2014731666. The cubic root of 991191975 is about 997.0553290911.

The spelling of 991191975 in words is "nine hundred ninety-one million, one hundred ninety-one thousand, nine hundred seventy-five".