9998991 has 16 divisors (see below), whose sum is σ = 15215200.
Its totient is φ = 6485184.
The previous prime is 9998977. The next prime is 9999047. The reversal of 9998991 is 1998999.
It can be divided in two parts, 999 and 8991, that multiplied together give a square (8982009 = 29972).
It is not a de Polignac number, because 9998991 - 29 = 9998479 is a prime.
It is a Duffinian number.
9998991 is a modest number, since divided by 8991 gives 999 as remainder.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (9998971) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (11) of ones.
It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4006 + ... + 6003.
It is an arithmetic number, because the mean of its divisors is an integer number (950950).
Almost surely, 29998991 is an apocalyptic number.
9998991 is a deficient number, since it is larger than the sum of its proper divisors (5216209).
9998991 is a wasteful number, since it uses less digits than its factorization.
9998991 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 10055 (or 10049 counting only the distinct ones).
The product of its digits is 472392, while the sum is 54.
The square root of 9998991 is about 3162.1181192359.
The cubic root of 9998991 is about 215.4362226775.
The spelling of 9998991 in words is "nine million, nine hundred ninety-eight thousand, nine hundred ninety-one".