91811957 has 2 divisors, whose sum is σ = 91811958. Its totient is φ = 91811956.

The previous prime is 91811947. The next prime is 91811959. The reversal of 91811957 is 75911819.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 91508356 + 303601 = 9566^2 + 551^2 .

It is a cyclic number.

It is not a de Polignac number, because 91811957 - 2¹⁴ = 91795573 is a prime.

Together with 91811959, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91811959) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45905978 + 45905979.

It is an arithmetic number, because the mean of its divisors is an integer number (45905979).

Almost surely, 2^91811957 is an apocalyptic number.

It is an amenable number.

91811957 is a deficient number, since it is larger than the sum of its proper divisors (1).

91811957 is an equidigital number, since it uses as much as digits as its factorization.

91811957 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 22680, while the sum is 41.

The square root of 91811957 is about 9581.8556136064. The cubic root of 91811957 is about 451.1279637152.

The spelling of 91811957 in words is "ninety-one million, eight hundred eleven thousand, nine hundred fifty-seven".