21245616 has 90 divisors (see below), whose sum is σ = 69188652. Its totient is φ = 6068160.

The previous prime is 21245561. The next prime is 21245617. The reversal of 21245616 is 61654212.

21245616 is a `hidden beast` number, since 2 + 1 + 2 + 45 + 616 = 666.

It is a self number, because there is not a number n which added to its sum of digits gives 21245616.

It is not an unprimeable number, because it can be changed into a prime (21245617) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 5551 + ... + 8561.

Almost surely, 2^21245616 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 21245616, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34594326).

21245616 is an abundant number, since it is smaller than the sum of its proper divisors (47943036).

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

21245616 is a wasteful number, since it uses less digits than its factorization.

21245616 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3039 (or 3023 counting only the distinct ones).

The product of its digits is 2880, while the sum is 27.

The square root of 21245616 is about 4609.2966925552. The cubic root of 21245616 is about 276.9638637929.

Adding to 21245616 its reverse (61654212), we get a palindrome (82899828).

The spelling of 21245616 in words is "twenty-one million, two hundred forty-five thousand, six hundred sixteen".