9981791 has 4 divisors (see below), whose sum is σ = 9988392. Its totient is φ = 9975192.

The previous prime is 9981787. The next prime is 9981799. The reversal of 9981791 is 1971899.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 1971899 = 397 ⋅4967.

It is a cyclic number.

It is not a de Polignac number, because 9981791 - 2² = 9981787 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9981799) 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, 221 + ... + 4473.

It is an arithmetic number, because the mean of its divisors is an integer number (2497098).

Almost surely, 2^9981791 is an apocalyptic number.

9981791 is a deficient number, since it is larger than the sum of its proper divisors (6601).

9981791 is a wasteful number, since it uses less digits than its factorization.

9981791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6600.

The product of its digits is 40824, while the sum is 44.

The square root of 9981791 is about 3159.3972526417. The cubic root of 9981791 is about 215.3126225473.

The spelling of 9981791 in words is "nine million, nine hundred eighty-one thousand, seven hundred ninety-one".