91819991 has 2 divisors, whose sum is σ = 91819992. Its totient is φ = 91819990.

The previous prime is 91819961. The next prime is 91820021. The reversal of 91819991 is 19991819.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (91819961) and next prime (91820021).

It is a cyclic number.

It is not a de Polignac number, because 91819991 - 2²² = 87625687 is a prime.

It is a Sophie Germain 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 (91819901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45909995 + 45909996.

It is an arithmetic number, because the mean of its divisors is an integer number (45909996).

Almost surely, 2^91819991 is an apocalyptic number.

91819991 is a deficient number, since it is larger than the sum of its proper divisors (1).

91819991 is an equidigital number, since it uses as much as digits as its factorization.

91819991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 52488, while the sum is 47.

The square root of 91819991 is about 9582.2748342969. The cubic root of 91819991 is about 451.1411219736.

The spelling of 91819991 in words is "ninety-one million, eight hundred nineteen thousand, nine hundred ninety-one".