999999990 has 192 divisors, whose sum is σ = 2924880192. Its totient is φ = 235008000.

The previous prime is 999999937. The next prime is 1000000007. The reversal of 999999990 is 99999999.

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 (19) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 7299202 + ... + 7299338.

It is an arithmetic number, because the mean of its divisors is an integer number (15233751).

Almost surely, 2^999999990 is an apocalyptic number.

999999990 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 999999990, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1462440096).

999999990 is an abundant number, since it is smaller than the sum of its proper divisors (1924880202).

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

999999990 is a wasteful number, since it uses less digits than its factorization.

999999990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 335 (or 332 counting only the distinct ones).

The product of its (nonzero) digits is 43046721, while the sum is 72.

The square root of 999999990 is about 31622.7764435699. The cubic root of 999999990 is about 999.9999966667. Note that the first 5 decimals are identical.

It can be divided in two parts, 9 and 99999990, that added together give a palindrome (99999999).

The spelling of 999999990 in words is "nine hundred ninety-nine million, nine hundred ninety-nine thousand, nine hundred ninety".