91007981 has 2 divisors, whose sum is σ = 91007982. Its totient is φ = 91007980.

The previous prime is 91007977. The next prime is 91007993. The reversal of 91007981 is 18970019.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 76825225 + 14182756 = 8765^2 + 3766^2 .

It is an emirp because it is prime and its reverse (18970019) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 91007981 - 2² = 91007977 is a prime.

It is a super-2 number, since 2×91007981² = 16564905211392722, which contains 22 as substring.

It is a Sophie Germain prime.

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 (91007911) 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, 45503990 + 45503991.

It is an arithmetic number, because the mean of its divisors is an integer number (45503991).

Almost surely, 2^91007981 is an apocalyptic number.

It is an amenable number.

91007981 is a deficient number, since it is larger than the sum of its proper divisors (1).

91007981 is an equidigital number, since it uses as much as digits as its factorization.

91007981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4536, while the sum is 35.

The square root of 91007981 is about 9539.8103230620. The cubic root of 91007981 is about 449.8072936196.

The spelling of 91007981 in words is "ninety-one million, seven thousand, nine hundred eighty-one".