91811809 has 2 divisors, whose sum is σ = 91811810. Its totient is φ = 91811808.

The previous prime is 91811789. The next prime is 91811813. The reversal of 91811809 is 90811819.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 78269409 + 13542400 = 8847^2 + 3680^2 .

It is a cyclic number.

It is not a de Polignac number, because 91811809 - 2¹¹ = 91809761 is a prime.

It is not a weakly prime, because it can be changed into another prime (91811309) 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, 45905904 + 45905905.

It is an arithmetic number, because the mean of its divisors is an integer number (45905905).

Almost surely, 2^91811809 is an apocalyptic number.

It is an amenable number.

91811809 is a deficient number, since it is larger than the sum of its proper divisors (1).

91811809 is an equidigital number, since it uses as much as digits as its factorization.

91811809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5184, while the sum is 37.

The square root of 91811809 is about 9581.8478906733. The cubic root of 91811809 is about 451.1277213104.

The spelling of 91811809 in words is "ninety-one million, eight hundred eleven thousand, eight hundred nine".