9947991 has 8 divisors (see below), whose sum is σ = 13349104. Its totient is φ = 6589440.

The previous prime is 9947969. The next prime is 9947999. The reversal of 9947991 is 1997499.

9947991 is nontrivially palindromic in base 12.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 9947991 - 2⁷ = 9947863 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 9947991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9947999) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10090 + ... + 11031.

It is an arithmetic number, because the mean of its divisors is an integer number (1668638).

Almost surely, 2^9947991 is an apocalyptic number.

9947991 is a deficient number, since it is larger than the sum of its proper divisors (3401113).

9947991 is a wasteful number, since it uses less digits than its factorization.

9947991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21281.

The product of its digits is 183708, while the sum is 48.

The square root of 9947991 is about 3154.0435951331. The cubic root of 9947991 is about 215.0693196344.

The spelling of 9947991 in words is "nine million, nine hundred forty-seven thousand, nine hundred ninety-one".