99990990 has 128 divisors (see below), whose sum is σ = 294243840. Its totient is φ = 23961600.

The previous prime is 99990973. The next prime is 99991009. The reversal of 99990990 is 9909999.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

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 63 ways as a sum of consecutive naturals, for example, 388942 + ... + 389198.

It is an arithmetic number, because the mean of its divisors is an integer number (2298780).

Almost surely, 2^99990990 is an apocalyptic number.

99990990 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 99990990, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (147121920).

99990990 is an abundant number, since it is smaller than the sum of its proper divisors (194252850).

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

99990990 is a wasteful number, since it uses less digits than its factorization.

99990990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 415 (or 409 counting only the distinct ones).

The product of its (nonzero) digits is 531441, while the sum is 54.

The square root of 99990990 is about 9999.5494898520. The cubic root of 99990990 is about 464.1449427041.

It can be divided in two parts, 999909 and 90, that added together give a palindrome (999999).

The spelling of 99990990 in words is "ninety-nine million, nine hundred ninety thousand, nine hundred ninety".