21647616 has 72 divisors (see below), whose sum is σ = 58572864. Its totient is φ = 7096320.

The previous prime is 21647609. The next prime is 21647617. The reversal of 21647616 is 61674612.

It is not an unprimeable number, because it can be changed into a prime (21647617) by changing a digit.

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, 54330 + ... + 54726.

It is an arithmetic number, because the mean of its divisors is an integer number (813512).

Almost surely, 2^21647616 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 21647616, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29286432).

21647616 is an abundant number, since it is smaller than the sum of its proper divisors (36925248).

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

21647616 is an equidigital number, since it uses as much as digits as its factorization.

21647616 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 487 (or 473 counting only the distinct ones).

The product of its digits is 12096, while the sum is 33.

The square root of 21647616 is about 4652.6998613708. The cubic root of 21647616 is about 278.6998223207.

The spelling of 21647616 in words is "twenty-one million, six hundred forty-seven thousand, six hundred sixteen".