91089721 has 2 divisors, whose sum is σ = 91089722. Its totient is φ = 91089720.

The previous prime is 91089709. The next prime is 91089727. The reversal of 91089721 is 12798019.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 84272400 + 6817321 = 9180^2 + 2611^2 .

It is a cyclic number.

It is not a de Polignac number, because 91089721 - 2⁹ = 91089209 is a prime.

It is equal to p_5276566 and since 91089721 and 5276566 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (91089727) 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, 45544860 + 45544861.

It is an arithmetic number, because the mean of its divisors is an integer number (45544861).

Almost surely, 2^91089721 is an apocalyptic number.

It is an amenable number.

91089721 is a deficient number, since it is larger than the sum of its proper divisors (1).

91089721 is an equidigital number, since it uses as much as digits as its factorization.

91089721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9072, while the sum is 37.

The square root of 91089721 is about 9544.0935137917. The cubic root of 91089721 is about 449.9419200762.

The spelling of 91089721 in words is "ninety-one million, eighty-nine thousand, seven hundred twenty-one".