21008916 has 24 divisors (see below), whose sum is σ = 54467840. Its totient is φ = 7002936.

The previous prime is 21008903. The next prime is 21008941. The reversal of 21008916 is 61980012.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a self number, because there is not a number n which added to its sum of digits gives 21008916.

It is a congruent number.

It is an unprimeable number.

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, 97156 + ... + 97371.

Almost surely, 2^21008916 is an apocalyptic number.

It is an amenable number.

21008916 is an abundant number, since it is smaller than the sum of its proper divisors (33458924).

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

21008916 is a wasteful number, since it uses less digits than its factorization.

21008916 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 194540 (or 194532 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 27.

The square root of 21008916 is about 4583.5484070750. The cubic root of 21008916 is about 275.9314574595.

Adding to 21008916 its reverse (61980012), we get a palindrome (82988928).

The spelling of 21008916 in words is "twenty-one million, eight thousand, nine hundred sixteen".