8091991 has 2 divisors, whose sum is σ = 8091992. Its totient is φ = 8091990.

The previous prime is 8091973. The next prime is 8092003. The reversal of 8091991 is 1991908.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 8091991 - 2⁵ = 8091959 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 8091991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (8091901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4045995 + 4045996.

It is an arithmetic number, because the mean of its divisors is an integer number (4045996).

Almost surely, 2^8091991 is an apocalyptic number.

8091991 is a deficient number, since it is larger than the sum of its proper divisors (1).

8091991 is an equidigital number, since it uses as much as digits as its factorization.

8091991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5832, while the sum is 37.

The square root of 8091991 is about 2844.6425082952. The cubic root of 8091991 is about 200.7636719808.

The spelling of 8091991 in words is "eight million, ninety-one thousand, nine hundred ninety-one".