21456828 has 72 divisors (see below), whose sum is σ = 56504448. Its totient is φ = 6860448.

The previous prime is 21456797. The next prime is 21456829. The reversal of 21456828 is 82865412.

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

It is a nialpdrome in base 9.

It is a junction number, because it is equal to n+sod(n) for n = 21456792 and 21456801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21456829) 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, 128401 + ... + 128567.

It is an arithmetic number, because the mean of its divisors is an integer number (784784).

Almost surely, 2^21456828 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 21456828, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28252224).

21456828 is an abundant number, since it is smaller than the sum of its proper divisors (35047620).

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

21456828 is a wasteful number, since it uses less digits than its factorization.

21456828 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 303 (or 298 counting only the distinct ones).

The product of its digits is 30720, while the sum is 36.

The square root of 21456828 is about 4632.1515519249. The cubic root of 21456828 is about 277.8786455133.

The spelling of 21456828 in words is "twenty-one million, four hundred fifty-six thousand, eight hundred twenty-eight".