91021181 has 2 divisors, whose sum is σ = 91021182. Its totient is φ = 91021180.

The previous prime is 91021171. The next prime is 91021201. The reversal of 91021181 is 18112019.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 55428025 + 35593156 = 7445^2 + 5966^2 .

It is an emirp because it is prime and its reverse (18112019) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 91021181 - 2¹⁸ = 90759037 is a prime.

It is a super-2 number, since 2×91021181² = 16569710781269522, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91021141) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45510590 + 45510591.

It is an arithmetic number, because the mean of its divisors is an integer number (45510591).

Almost surely, 2^91021181 is an apocalyptic number.

It is an amenable number.

91021181 is a deficient number, since it is larger than the sum of its proper divisors (1).

91021181 is an equidigital number, since it uses as much as digits as its factorization.

91021181 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 144, while the sum is 23.

The square root of 91021181 is about 9540.5021356321. The cubic root of 91021181 is about 449.8290395851.

The spelling of 91021181 in words is "ninety-one million, twenty-one thousand, one hundred eighty-one".