9881991 has 24 divisors (see below), whose sum is σ = 16408704. Its totient is φ = 5613840.

The previous prime is 9881987. The next prime is 9881999. The reversal of 9881991 is 1991889.

9881991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 9881991 - 2² = 9881987 is a prime.

It is a super-2 number, since 2×9881991² = 195307492248162, which contains 22 as substring.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9881999) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 13956 + ... + 14646.

It is an arithmetic number, because the mean of its divisors is an integer number (683696).

Almost surely, 2^9881991 is an apocalyptic number.

9881991 is a deficient number, since it is larger than the sum of its proper divisors (6526713).

9881991 is a wasteful number, since it uses less digits than its factorization.

9881991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 931 (or 928 counting only the distinct ones).

The product of its digits is 46656, while the sum is 45.

The square root of 9881991 is about 3143.5634238870. The cubic root of 9881991 is about 214.5926377047.

The spelling of 9881991 in words is "nine million, eight hundred eighty-one thousand, nine hundred ninety-one".