21008889 has 80 divisors (see below), whose sum is σ = 38681280. Its totient is φ = 11197440.

The previous prime is 21008887. The next prime is 21008893. The reversal of 21008889 is 98880012.

It is not a de Polignac number, because 21008889 - 2¹ = 21008887 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21008887) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 287757 + ... + 287829.

It is an arithmetic number, because the mean of its divisors is an integer number (483516).

Almost surely, 2^21008889 is an apocalyptic number.

It is an amenable number.

21008889 is a deficient number, since it is larger than the sum of its proper divisors (17672391).

21008889 is a wasteful number, since it uses less digits than its factorization.

21008889 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132 (or 123 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 36.

The square root of 21008889 is about 4583.5454617577. The cubic root of 21008889 is about 275.9313392533.

The spelling of 21008889 in words is "twenty-one million, eight thousand, eight hundred eighty-nine".