9991751 has 8 divisors (see below), whose sum is σ = 12457344. Its totient is φ = 7785720.

The previous prime is 9991727. The next prime is 9991757. The reversal of 9991751 is 1571999.

It is a happy number.

9991751 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a cyclic number.

It is not a de Polignac number, because 9991751 - 2¹⁰ = 9990727 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 9991699 and 9991708.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9991757) 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, 64805 + ... + 64958.

It is an arithmetic number, because the mean of its divisors is an integer number (1557168).

Almost surely, 2^9991751 is an apocalyptic number.

9991751 is a deficient number, since it is larger than the sum of its proper divisors (2465593).

9991751 is a wasteful number, since it uses less digits than its factorization.

9991751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129781.

The product of its digits is 25515, while the sum is 41.

The square root of 9991751 is about 3160.9731096610. The cubic root of 9991751 is about 215.3842129342.

The spelling of 9991751 in words is "nine million, nine hundred ninety-one thousand, seven hundred fifty-one".