991749191 has 2 divisors, whose sum is σ = 991749192. Its totient is φ = 991749190.

The previous prime is 991749181. The next prime is 991749263. The reversal of 991749191 is 191947199.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 991749191 - 2¹⁰ = 991748167 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991749181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495874595 + 495874596.

It is an arithmetic number, because the mean of its divisors is an integer number (495874596).

Almost surely, 2^991749191 is an apocalyptic number.

991749191 is a deficient number, since it is larger than the sum of its proper divisors (1).

991749191 is an equidigital number, since it uses as much as digits as its factorization.

991749191 is an evil number, because the sum of its binary digits is even.

The product of its digits is 183708, while the sum is 50.

The square root of 991749191 is about 31492.0496474904. The cubic root of 991749191 is about 997.2421314866.

The spelling of 991749191 in words is "nine hundred ninety-one million, seven hundred forty-nine thousand, one hundred ninety-one".