99999990 has 48 divisors (see below), whose sum is σ = 261144000.
Its totient is φ = 26549376.
The previous prime is 99999989. The next prime is 100000007. The reversal of 99999990 is 9999999.
It is a nialpdrome in base 10.
It is a congruent number.
It is an unprimeable number.
It is a pernicious number, because its binary representation contains a prime number (17) of ones.
It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 19186 + ... + 23834.
It is an arithmetic number, because the mean of its divisors is an integer number (5440500).
Almost surely, 299999990 is an apocalyptic number.
99999990 is a gapful number since it is divisible by the number (90) formed by its first and last digit.
99999990 is an abundant number, since it is smaller than the sum of its proper divisors (161144010).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
99999990 is a wasteful number, since it uses less digits than its factorization.
99999990 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 4901 (or 4898 counting only the distinct ones).
The product of its (nonzero) digits is 4782969, while the sum is 63.
The square root of 99999990 is about 9999.9995000000.
Note that the first 3 decimals coincide.
The cubic root of 99999990 is about 464.1588678893.
It can be divided in two parts, 9 and 9999990, that added together give a palindrome (9999999).
The spelling of 99999990 in words is "ninety-nine million, nine hundred ninety-nine thousand, nine hundred ninety".