9900 has 54 divisors (see below), whose sum is σ = 33852. Its totient is φ = 2400.

The previous prime is 9887. The next prime is 9901. The reversal of 9900 is 99.

9900 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.

It is a plaindrome in base 13 and base 16.

It is a nialpdrome in base 10.

It is a zygodrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (9901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 895 + ... + 905.

2⁹⁹⁰⁰ is an apocalyptic number.

9900 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

It is a pronic number, being equal to 99×100.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 9900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (16926).

9900 is an abundant number, since it is smaller than the sum of its proper divisors (23952).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

9900 is a wasteful number, since it uses less digits than its factorization.

9900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31 (or 21 counting only the distinct ones).

The product of its (nonzero) digits is 81, while the sum is 18.

The square root of 9900 is about 99.4987437107. The cubic root of 9900 is about 21.4722916902.

Adding to 9900 its reverse (99), we get a palindrome (9999).

Subtracting from 9900 its reverse (99), we obtain a square (9801 = 99²).

Multiplying 9900 by its reverse (99), we get a square (980100 = 990²).

9900 divided by its reverse (99) gives a square (100 = 10²).

It can be divided in two parts, 9 and 900, that multiplied together give a square (8100 = 90²).

The spelling of 9900 in words is "nine thousand, nine hundred".