9991571 has 2 divisors, whose sum is σ = 9991572. Its totient is φ = 9991570.

The previous prime is 9991567. The next prime is 9991603. The reversal of 9991571 is 1751999.

It is a happy number.

9991571 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 9991571 - 2² = 9991567 is a prime.

It is not a weakly prime, because it can be changed into another prime (9991771) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4995785 + 4995786.

It is an arithmetic number, because the mean of its divisors is an integer number (4995786).

Almost surely, 2^9991571 is an apocalyptic number.

9991571 is a deficient number, since it is larger than the sum of its proper divisors (1).

9991571 is an equidigital number, since it uses as much as digits as its factorization.

9991571 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25515, while the sum is 41.

The square root of 9991571 is about 3160.9446372880. The cubic root of 9991571 is about 215.3829195543.

The spelling of 9991571 in words is "nine million, nine hundred ninety-one thousand, five hundred seventy-one".