9991531 has 4 divisors (see below), whose sum is σ = 10899864. Its totient is φ = 9083200.

The previous prime is 9991489. The next prime is 9991543. The reversal of 9991531 is 1351999.

9991531 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 9991531 - 2¹³ = 9983339 is a prime.

It is a super-3 number, since 3×9991531³ (a number of 22 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (9991571) 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 in 3 ways as a sum of consecutive naturals, for example, 454150 + ... + 454171.

It is an arithmetic number, because the mean of its divisors is an integer number (2724966).

Almost surely, 2^9991531 is an apocalyptic number.

9991531 is a deficient number, since it is larger than the sum of its proper divisors (908333).

9991531 is a wasteful number, since it uses less digits than its factorization.

9991531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 908332.

The product of its digits is 10935, while the sum is 37.

The square root of 9991531 is about 3160.9383100592. The cubic root of 9991531 is about 215.3826321344.

The spelling of 9991531 in words is "nine million, nine hundred ninety-one thousand, five hundred thirty-one".