9991791 has 12 divisors (see below), whose sum is σ = 14531400. Its totient is φ = 6615600.

The previous prime is 9991771. The next prime is 9991811. The reversal of 9991791 is 1971999.

It is an interprime number because it is at equal distance from previous prime (9991771) and next prime (9991811).

It is not a de Polignac number, because 9991791 - 2⁶ = 9991727 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9991711) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2385 + ... + 5066.

It is an arithmetic number, because the mean of its divisors is an integer number (1210950).

Almost surely, 2^9991791 is an apocalyptic number.

9991791 is a deficient number, since it is larger than the sum of its proper divisors (4539609).

9991791 is a wasteful number, since it uses less digits than its factorization.

9991791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7606 (or 7603 counting only the distinct ones).

The product of its digits is 45927, while the sum is 45.

The square root of 9991791 is about 3160.9794368202. The cubic root of 9991791 is about 215.3845003499.

The spelling of 9991791 in words is "nine million, nine hundred ninety-one thousand, seven hundred ninety-one".