9931391 has 4 divisors (see below), whose sum is σ = 9952272. Its totient is φ = 9910512.

The previous prime is 9931381. The next prime is 9931393. The reversal of 9931391 is 1931399.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-9931391 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9931393) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9710 + ... + 10683.

It is an arithmetic number, because the mean of its divisors is an integer number (2488068).

Almost surely, 2^9931391 is an apocalyptic number.

9931391 is the 1685-th centered heptagonal number.

9931391 is a deficient number, since it is larger than the sum of its proper divisors (20881).

9931391 is a wasteful number, since it uses less digits than its factorization.

9931391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20880.

The product of its digits is 6561, while the sum is 35.

The square root of 9931391 is about 3151.4109538427. The cubic root of 9931391 is about 214.9496258403.

The spelling of 9931391 in words is "nine million, nine hundred thirty-one thousand, three hundred ninety-one".