991323250091 has 2 divisors, whose sum is σ = 991323250092. Its totient is φ = 991323250090.

The previous prime is 991323250051. The next prime is 991323250117. The reversal of 991323250091 is 190052323199.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 991323250091 - 2¹⁸ = 991322987947 is a prime.

It is not a weakly prime, because it can be changed into another prime (991323250051) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495661625045 + 495661625046.

It is an arithmetic number, because the mean of its divisors is an integer number (495661625046).

Almost surely, 2^991323250091 is an apocalyptic number.

991323250091 is a deficient number, since it is larger than the sum of its proper divisors (1).

991323250091 is an equidigital number, since it uses as much as digits as its factorization.

991323250091 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 131220, while the sum is 44.

The spelling of 991323250091 in words is "nine hundred ninety-one billion, three hundred twenty-three million, two hundred fifty thousand, ninety-one".