99999980 has 12 divisors (see below), whose sum is σ = 210000000.
Its totient is φ = 39999984.
The previous prime is 99999971. The next prime is 99999989. The reversal of 99999980 is 8999999.
It is an interprime number because it is at equal distance from previous prime (99999971) and next prime (99999989).
It is a nialpdrome in base 10.
It is not an unprimeable number, because it can be changed into a prime (99999989) 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, 2499980 + ... + 2500019.
It is an arithmetic number, because the mean of its divisors is an integer number (17500000).
Almost surely, 299999980 is an apocalyptic number.
It is an amenable number.
99999980 is an abundant number, since it is smaller than the sum of its proper divisors (110000020).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
99999980 is a wasteful number, since it uses less digits than its factorization.
99999980 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 5000008 (or 5000006 counting only the distinct ones).
The product of its (nonzero) digits is 4251528, while the sum is 62.
The square root of 99999980 is about 9999.9989999999.
The cubic root of 99999980 is about 464.1588524174.
The spelling of 99999980 in words is "ninety-nine million, nine hundred ninety-nine thousand, nine hundred eighty".