9991438531 has 2 divisors, whose sum is σ = 9991438532. Its totient is φ = 9991438530.

The previous prime is 9991438529. The next prime is 9991438549. The reversal of 9991438531 is 1358341999.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 9991438531 - 2¹ = 9991438529 is a prime.

It is a super-2 number, since 2×9991438531² (a number of 21 digits) contains 22 as substring.

Together with 9991438529, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (9991438031) 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, 4995719265 + 4995719266.

It is an arithmetic number, because the mean of its divisors is an integer number (4995719266).

Almost surely, 2^9991438531 is an apocalyptic number.

9991438531 is a deficient number, since it is larger than the sum of its proper divisors (1).

9991438531 is an equidigital number, since it uses as much as digits as its factorization.

9991438531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1049760, while the sum is 52.

The square root of 9991438531 is about 99957.1834887318. The cubic root of 9991438531 is about 2153.8196769576.

The spelling of 9991438531 in words is "nine billion, nine hundred ninety-one million, four hundred thirty-eight thousand, five hundred thirty-one".