9991491 has 4 divisors (see below), whose sum is σ = 13321992. Its totient is φ = 6660992.

The previous prime is 9991489. The next prime is 9991543. The reversal of 9991491 is 1941999.

9991491 is nontrivially palindromic in base 12.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1941999 = 3 ⋅647333.

It is a cyclic number.

It is not a de Polignac number, because 9991491 - 2¹ = 9991489 is a prime.

9991491 is a lucky number.

It is a nialpdrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (9991441) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1665246 + ... + 1665251.

It is an arithmetic number, because the mean of its divisors is an integer number (3330498).

Almost surely, 2^9991491 is an apocalyptic number.

9991491 is a deficient number, since it is larger than the sum of its proper divisors (3330501).

9991491 is a wasteful number, since it uses less digits than its factorization.

9991491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3330500.

The product of its digits is 26244, while the sum is 42.

The square root of 9991491 is about 3160.9319828177. The cubic root of 9991491 is about 215.3823447138.

The spelling of 9991491 in words is "nine million, nine hundred ninety-one thousand, four hundred ninety-one".