91688921 has 2 divisors, whose sum is σ = 91688922. Its totient is φ = 91688920.

The previous prime is 91688899. The next prime is 91688929. The reversal of 91688921 is 12988619.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 62410000 + 29278921 = 7900^2 + 5411^2 .

It is a cyclic number.

It is not a de Polignac number, because 91688921 - 2²⁶ = 24580057 is a prime.

It is not a weakly prime, because it can be changed into another prime (91688929) 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, 45844460 + 45844461.

It is an arithmetic number, because the mean of its divisors is an integer number (45844461).

Almost surely, 2^91688921 is an apocalyptic number.

It is an amenable number.

91688921 is a deficient number, since it is larger than the sum of its proper divisors (1).

91688921 is an equidigital number, since it uses as much as digits as its factorization.

91688921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 62208, while the sum is 44.

The square root of 91688921 is about 9575.4332016886. The cubic root of 91688921 is about 450.9263567413.

The spelling of 91688921 in words is "ninety-one million, six hundred eighty-eight thousand, nine hundred twenty-one".