91871861 has 2 divisors, whose sum is σ = 91871862. Its totient is φ = 91871860.

The previous prime is 91871833. The next prime is 91871863. The reversal of 91871861 is 16817819.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 77545636 + 14326225 = 8806^2 + 3785^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-91871861 is a prime.

It is a Sophie Germain prime.

Together with 91871863, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91871863) 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, 45935930 + 45935931.

It is an arithmetic number, because the mean of its divisors is an integer number (45935931).

Almost surely, 2^91871861 is an apocalyptic number.

It is an amenable number.

91871861 is a deficient number, since it is larger than the sum of its proper divisors (1).

91871861 is an equidigital number, since it uses as much as digits as its factorization.

91871861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 24192, while the sum is 41.

The square root of 91871861 is about 9584.9810119791. The cubic root of 91871861 is about 451.2260573081.

The spelling of 91871861 in words is "ninety-one million, eight hundred seventy-one thousand, eight hundred sixty-one".