21216768 has 80 divisors (see below), whose sum is σ = 59579520. Its totient is φ = 6690816.

The previous prime is 21216751. The next prime is 21216773. The reversal of 21216768 is 86761212.

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, 28821 + ... + 29547.

It is an arithmetic number, because the mean of its divisors is an integer number (744744).

Almost surely, 2^21216768 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 21216768, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29789760).

21216768 is an abundant number, since it is smaller than the sum of its proper divisors (38362752).

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

21216768 is an equidigital number, since it uses as much as digits as its factorization.

21216768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 767 (or 751 counting only the distinct ones).

The product of its digits is 8064, while the sum is 33.

The square root of 21216768 is about 4606.1663018176. The cubic root of 21216768 is about 276.8384501144.

The spelling of 21216768 in words is "twenty-one million, two hundred sixteen thousand, seven hundred sixty-eight".