9991421591 has 8 divisors (see below), whose sum is σ = 10354865520. Its totient is φ = 9629238528.

The previous prime is 9991421581. The next prime is 9991421641. The reversal of 9991421591 is 1951241999.

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 9991421591 - 2¹⁰ = 9991420567 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 (9991421581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 299066 + ... + 330791.

It is an arithmetic number, because the mean of its divisors is an integer number (1294358190).

Almost surely, 2^9991421591 is an apocalyptic number.

9991421591 is a deficient number, since it is larger than the sum of its proper divisors (363443929).

9991421591 is a wasteful number, since it uses less digits than its factorization.

9991421591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 630433.

The product of its digits is 262440, while the sum is 50.

The square root of 9991421591 is about 99957.0987524148. The cubic root of 9991421591 is about 2153.8184597246.

The spelling of 9991421591 in words is "nine billion, nine hundred ninety-one million, four hundred twenty-one thousand, five hundred ninety-one".