9999981 has 12 divisors (see below), whose sum is σ = 14483040.
Its totient is φ = 6648840.
The previous prime is 9999973. The next prime is 9999991. The reversal of 9999981 is 1899999.
It can be divided in two parts, 999998 and 1, that added together give a palindrome (999999).
9999981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.
It is not a de Polignac number, because 9999981 - 23 = 9999973 is a prime.
It is a super-2 number, since 2×99999812 = 199999240000722, which contains 22 as substring.
It is a Curzon number.
It is a nialpdrome in base 10.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (9999901) by changing a digit.
It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2686 + ... + 5216.
It is an arithmetic number, because the mean of its divisors is an integer number (1206920).
Almost surely, 29999981 is an apocalyptic number.
It is an amenable number.
9999981 is a deficient number, since it is larger than the sum of its proper divisors (4483059).
9999981 is a wasteful number, since it uses less digits than its factorization.
9999981 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 2976 (or 2973 counting only the distinct ones).
The product of its digits is 472392, while the sum is 54.
The square root of 9999981 is about 3162.2746560032.
The cubic root of 9999981 is about 215.4433325556.
The spelling of 9999981 in words is "nine million, nine hundred ninety-nine thousand, nine hundred eighty-one".