21516768 has 144 divisors (see below), whose sum is σ = 75400416. Its totient is φ = 5667840.

The previous prime is 21516767. The next prime is 21516791. The reversal of 21516768 is 86761512.

It is a tau number, because it is divible by the number of its divisors (144).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21516767) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 25798 + ... + 26618.

It is an arithmetic number, because the mean of its divisors is an integer number (523614).

Almost surely, 2^21516768 is an apocalyptic number.

21516768 is a gapful number since it is divisible by the number (28) 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 21516768, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37700208).

21516768 is an abundant number, since it is smaller than the sum of its proper divisors (53883648).

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

21516768 is a wasteful number, since it uses less digits than its factorization.

21516768 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 857 (or 846 counting only the distinct ones).

The product of its digits is 20160, while the sum is 36.

The square root of 21516768 is about 4638.6170352811. The cubic root of 21516768 is about 278.1371577903.

The spelling of 21516768 in words is "twenty-one million, five hundred sixteen thousand, seven hundred sixty-eight".