21289668 has 12 divisors (see below), whose sum is σ = 49675920. Its totient is φ = 7096552.

The previous prime is 21289643. The next prime is 21289669. The reversal of 21289668 is 86698212.

It is a tau number, because it is divible by the number of its divisors (12).

It is not an unprimeable number, because it can be changed into a prime (21289669) 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 3 ways as a sum of consecutive naturals, for example, 887058 + ... + 887081.

It is an arithmetic number, because the mean of its divisors is an integer number (4139660).

Almost surely, 2^21289668 is an apocalyptic number.

It is an amenable number.

21289668 is an abundant number, since it is smaller than the sum of its proper divisors (28386252).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21289668 is a wasteful number, since it uses less digits than its factorization.

21289668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1774146 (or 1774144 counting only the distinct ones).

The product of its digits is 82944, while the sum is 42.

The square root of 21289668 is about 4614.0728212719. The cubic root of 21289668 is about 277.1551564214.

The spelling of 21289668 in words is "twenty-one million, two hundred eighty-nine thousand, six hundred sixty-eight".