21616320 has 224 divisors, whose sum is σ = 79004160. Its totient is φ = 4956160.

The previous prime is 21616303. The next prime is 21616327. The reversal of 21616320 is 2361612.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21616327) 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 31 ways as a sum of consecutive naturals, for example, 242836 + ... + 242924.

Almost surely, 2^21616320 is an apocalyptic number.

21616320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21616320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39502080).

21616320 is an abundant number, since it is smaller than the sum of its proper divisors (57387840).

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

21616320 is a wasteful number, since it uses less digits than its factorization.

21616320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 143 (or 133 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 21616320 is about 4649.3354363823. The cubic root of 21616320 is about 278.5654519240.

Adding to 21616320 its reverse (2361612), we get a palindrome (23977932).

The spelling of 21616320 in words is "twenty-one million, six hundred sixteen thousand, three hundred twenty".