99999920 has 20 divisors (see below), whose sum is σ = 232500000.
Its totient is φ = 39999936.
The previous prime is 99999847. The next prime is 99999931. The reversal of 99999920 is 2999999.
It is a happy number.
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 (56) coincides with the sum of the digits of its prime factors.
It is a nialpdrome in base 10.
It is a congruent number.
It is an unprimeable number.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 624920 + ... + 625079.
It is an arithmetic number, because the mean of its divisors is an integer number (11625000).
Almost surely, 299999920 is an apocalyptic number.
It is an amenable number.
99999920 is an abundant number, since it is smaller than the sum of its proper divisors (132500080).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
99999920 is a wasteful number, since it uses less digits than its factorization.
99999920 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 1250012 (or 1250006 counting only the distinct ones).
The product of its (nonzero) digits is 1062882, while the sum is 56.
The square root of 99999920 is about 9999.9959999992.
The cubic root of 99999920 is about 464.1587595855.
The spelling of 99999920 in words is "ninety-nine million, nine hundred ninety-nine thousand, nine hundred twenty".