291091991 has 2 divisors, whose sum is σ = 291091992. Its totient is φ = 291091990.

The previous prime is 291091981. The next prime is 291092023. The reversal of 291091991 is 199190192.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 291091991 - 2¹⁴ = 291075607 is a prime.

It is a Chen prime.

It is equal to p_15795563 and since 291091991 and 15795563 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (291091921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 145545995 + 145545996.

It is an arithmetic number, because the mean of its divisors is an integer number (145545996).

Almost surely, 2^291091991 is an apocalyptic number.

291091991 is a deficient number, since it is larger than the sum of its proper divisors (1).

291091991 is an equidigital number, since it uses as much as digits as its factorization.

291091991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 13122, while the sum is 41.

The square root of 291091991 is about 17061.4182001380. The cubic root of 291091991 is about 662.7403592553.

The spelling of 291091991 in words is "two hundred ninety-one million, ninety-one thousand, nine hundred ninety-one".