99999921 has 16 divisors (see below), whose sum is σ = 152699904. Its totient is φ = 57023184.

The previous prime is 99999847. The next prime is 99999931. The reversal of 99999921 is 12999999.

It is not a de Polignac number, because 99999921 - 2¹¹ = 99997873 is a prime.

It is a nialpdrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (99999931) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5830 + ... + 15296.

It is an arithmetic number, because the mean of its divisors is an integer number (9543744).

Almost surely, 2^99999921 is an apocalyptic number.

It is an amenable number.

99999921 is a deficient number, since it is larger than the sum of its proper divisors (52699983).

99999921 is a wasteful number, since it uses less digits than its factorization.

99999921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9980.

The product of its digits is 1062882, while the sum is 57.

The square root of 99999921 is about 9999.9960499992. The cubic root of 99999921 is about 464.1587611327.

The spelling of 99999921 in words is "ninety-nine million, nine hundred ninety-nine thousand, nine hundred twenty-one".