9090 is an esthetic number in base 14, because in such base its adjacent digits differ by 1.
It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.
It is an alternating number because its digits alternate between odd and even.
9090 is an undulating number in base 10.
It is a Curzon number.
29090 is an apocalyptic number.
9090 is a gapful number since it is divisible by the number (90) formed by its first and last digit.
It is a practical number, because each smaller number is the sum of distinct divisors of 9090, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (11934).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
9090 is a wasteful number, since it uses less digits than its factorization.
9090 is an odious number, because the sum of its binary digits is odd.
The square root of 9090 is about 95.3414914924. The cubic root of 9090 is about 20.8699445130.
9090 divided by its sum of digits (18) gives a palindrome (505).
Subtracting from 9090 its product of nonzero digits (81), we obtain a palindrome (9009).
Adding to 9090 its reverse (909), we get a palindrome (9999).
The spelling of 9090 in words is "nine thousand, ninety".