21316624 has 40 divisors (see below), whose sum is σ = 48836160. Its totient is φ = 8819328.

The previous prime is 21316619. The next prime is 21316639. The reversal of 21316624 is 42661312.

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, 34 + ... + 6529.

It is an arithmetic number, because the mean of its divisors is an integer number (1220904).

Almost surely, 2^21316624 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21316624, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24418080).

21316624 is an abundant number, since it is smaller than the sum of its proper divisors (27519536).

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

21316624 is a wasteful number, since it uses less digits than its factorization.

21316624 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6607 (or 6601 counting only the distinct ones).

The product of its digits is 1728, while the sum is 25.

The square root of 21316624 is about 4616.9929607917. The cubic root of 21316624 is about 277.2720807979.

Adding to 21316624 its reverse (42661312), we get a palindrome (63977936).

The spelling of 21316624 in words is "twenty-one million, three hundred sixteen thousand, six hundred twenty-four".