999999920 has 20 divisors (see below), whose sum is σ = 2325000000.
Its totient is φ = 399999936.
The previous prime is 999999893. The next prime is 999999929. The reversal of 999999920 is 29999999.
It is a tau number, because it is divible by the number of its divisors (20).
It is a Smith number, since the sum of its digits (65) coincides with the sum of the digits of its prime factors.
It is a nialpdrome in base 10.
It is not an unprimeable number, because it can be changed into a prime (999999929) by changing a digit.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6249920 + ... + 6250079.
It is an arithmetic number, because the mean of its divisors is an integer number (116250000).
Almost surely, 2999999920 is an apocalyptic number.
It is an amenable number.
999999920 is an abundant number, since it is smaller than the sum of its proper divisors (1325000080).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
999999920 is a wasteful number, since it uses less digits than its factorization.
999999920 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 12500012 (or 12500006 counting only the distinct ones).
The product of its (nonzero) digits is 9565938, while the sum is 65.
The square root of 999999920 is about 31622.7753367727.
The cubic root of 999999920 is about 999.9999733333.
Note that the first 4 decimals are identical.
The spelling of 999999920 in words is "nine hundred ninety-nine million, nine hundred ninety-nine thousand, nine hundred twenty".