9951991 has 8 divisors (see below), whose sum is σ = 11972480. Its totient is φ = 8081208.

The previous prime is 9951973. The next prime is 9952037. The reversal of 9951991 is 1991599.

9951991 is digitally balanced in base 3, 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 9951991 - 2¹¹ = 9949943 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 (9951911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 37281 + ... + 37546.

It is an arithmetic number, because the mean of its divisors is an integer number (1496560).

Almost surely, 2^9951991 is an apocalyptic number.

9951991 is a deficient number, since it is larger than the sum of its proper divisors (2020489).

9951991 is a wasteful number, since it uses less digits than its factorization.

9951991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74853.

The product of its digits is 32805, while the sum is 43.

The square root of 9951991 is about 3154.6776380480. The cubic root of 9951991 is about 215.0981416013.

It can be divided in two parts, 995 and 1991, that multiplied together give a triangular number (1981045 = T₁₉₉₀).

The spelling of 9951991 in words is "nine million, nine hundred fifty-one thousand, nine hundred ninety-one".