21668328 has 96 divisors (see below), whose sum is σ = 64864800. Its totient is φ = 6480000.

The previous prime is 21668327. The next prime is 21668389. The reversal of 21668328 is 82386612.

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

It is a nude number because it is divisible by every one of its digits.

It is a junction number, because it is equal to n+sod(n) for n = 21668292 and 21668301.

It is not an unprimeable number, because it can be changed into a prime (21668327) 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 23 ways as a sum of consecutive naturals, for example, 86203 + ... + 86453.

It is an arithmetic number, because the mean of its divisors is an integer number (675675).

It is a vampire number, since it can be written as 2616 ⋅ 8283 (with its own digits).

Almost surely, 2^21668328 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 21668328, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32432400).

21668328 is an abundant number, since it is smaller than the sum of its proper divisors (43196472).

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

21668328 is a wasteful number, since it uses less digits than its factorization.

21668328 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 383 (or 376 counting only the distinct ones).

The product of its digits is 27648, while the sum is 36.

The square root of 21668328 is about 4654.9251336622. The cubic root of 21668328 is about 278.7886787674.

The spelling of 21668328 in words is "twenty-one million, six hundred sixty-eight thousand, three hundred twenty-eight".