99921 has 8 divisors (see below), whose sum is σ = 140320. Its totient is φ = 63072.

The previous prime is 99907. The next prime is 99923. The reversal of 99921 is 12999.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 99921 - 2⁷ = 99793 is a prime.

It is a Duffinian number.

99921 is a lucky number.

It is a nialpdrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (99923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 820 + ... + 933.

It is an arithmetic number, because the mean of its divisors is an integer number (17540).

2⁹⁹⁹²¹ is an apocalyptic number.

It is an amenable number.

99921 is a deficient number, since it is larger than the sum of its proper divisors (40399).

99921 is a wasteful number, since it uses less digits than its factorization.

99921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1775.

The product of its digits is 1458, while the sum is 30.

The square root of 99921 is about 316.1028313698. The cubic root of 99921 is about 46.4036622654.

The spelling of 99921 in words is "ninety-nine thousand, nine hundred twenty-one".