991521493 has 2 divisors, whose sum is σ = 991521494. Its totient is φ = 991521492.

The previous prime is 991521469. The next prime is 991521527. The reversal of 991521493 is 394125199.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 932508369 + 59013124 = 30537^2 + 7682^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-991521493 is a prime.

It is a super-2 number, since 2×991521493² = 1966229742161898098, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991528493) 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, 495760746 + 495760747.

It is an arithmetic number, because the mean of its divisors is an integer number (495760747).

Almost surely, 2^991521493 is an apocalyptic number.

It is an amenable number.

991521493 is a deficient number, since it is larger than the sum of its proper divisors (1).

991521493 is an equidigital number, since it uses as much as digits as its factorization.

991521493 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 87480, while the sum is 43.

The square root of 991521493 is about 31488.4342735551. The cubic root of 991521493 is about 997.1658059327.

The spelling of 991521493 in words is "nine hundred ninety-one million, five hundred twenty-one thousand, four hundred ninety-three".