91491989 has 2 divisors, whose sum is σ = 91491990. Its totient is φ = 91491988.

The previous prime is 91491947. The next prime is 91492001. The reversal of 91491989 is 98919419.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 91049764 + 442225 = 9542^2 + 665^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-91491989 is a prime.

It is a super-2 number, since 2×91491989² = 16741568102352242, 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 (91491929) 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, 45745994 + 45745995.

It is an arithmetic number, because the mean of its divisors is an integer number (45745995).

Almost surely, 2^91491989 is an apocalyptic number.

It is an amenable number.

91491989 is a deficient number, since it is larger than the sum of its proper divisors (1).

91491989 is an equidigital number, since it uses as much as digits as its factorization.

91491989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 209952, while the sum is 50.

The square root of 91491989 is about 9565.1444840107. The cubic root of 91491989 is about 450.6032879660.

The spelling of 91491989 in words is "ninety-one million, four hundred ninety-one thousand, nine hundred eighty-nine".