21647968 has 48 divisors (see below), whose sum is σ = 45239040. Its totient is φ = 10175616.

The previous prime is 21647957. The next prime is 21647993. The reversal of 21647968 is 86974612.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 49093 + ... + 49531.

It is an arithmetic number, because the mean of its divisors is an integer number (942480).

Almost surely, 2^21647968 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 21647968, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22619520).

21647968 is an abundant number, since it is smaller than the sum of its proper divisors (23591072).

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

21647968 is a wasteful number, since it uses less digits than its factorization.

21647968 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 539 (or 531 counting only the distinct ones).

The product of its digits is 145152, while the sum is 43.

The square root of 21647968 is about 4652.7376887162. The cubic root of 21647968 is about 278.7013329074.

It can be divided in two parts, 216 and 47968, that added together give a palindrome (48184).

The spelling of 21647968 in words is "twenty-one million, six hundred forty-seven thousand, nine hundred sixty-eight".