91031921 has 2 divisors, whose sum is σ = 91031922. Its totient is φ = 91031920.

The previous prime is 91031911. The next prime is 91031971. The reversal of 91031921 is 12913019.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 75342400 + 15689521 = 8680^2 + 3961^2 .

It is a cyclic number.

It is not a de Polignac number, because 91031921 - 2¹⁰ = 91030897 is a prime.

It is not a weakly prime, because it can be changed into another prime (91031911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45515960 + 45515961.

It is an arithmetic number, because the mean of its divisors is an integer number (45515961).

Almost surely, 2^91031921 is an apocalyptic number.

It is an amenable number.

91031921 is a deficient number, since it is larger than the sum of its proper divisors (1).

91031921 is an equidigital number, since it uses as much as digits as its factorization.

91031921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 486, while the sum is 26.

The square root of 91031921 is about 9541.0649824849. The cubic root of 91031921 is about 449.8467313422.

The spelling of 91031921 in words is "ninety-one million, thirty-one thousand, nine hundred twenty-one".