21168828 has 36 divisors (see below), whose sum is σ = 54119520. Its totient is φ = 6975936.

The previous prime is 21168827. The next prime is 21168871. The reversal of 21168828 is 82886112.

It is a tau number, because it is divible by the number of its divisors (36).

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

It is a junction number, because it is equal to n+sod(n) for n = 21168792 and 21168801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21168821) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 100 + ... + 6507.

It is an arithmetic number, because the mean of its divisors is an integer number (1503320).

Almost surely, 2^21168828 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 21168828, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27059760).

21168828 is an abundant number, since it is smaller than the sum of its proper divisors (32950692).

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

21168828 is a wasteful number, since it uses less digits than its factorization.

21168828 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6706 (or 6701 counting only the distinct ones).

The product of its digits is 12288, while the sum is 36.

The square root of 21168828 is about 4600.9594651551. The cubic root of 21168828 is about 276.6297842804.

The spelling of 21168828 in words is "twenty-one million, one hundred sixty-eight thousand, eight hundred twenty-eight".