21028668 has 48 divisors (see below), whose sum is σ = 52080000. Its totient is φ = 6585408.

The previous prime is 21028663. The next prime is 21028673. The reversal of 21028668 is 86682012.

It is an interprime number because it is at equal distance from previous prime (21028663) and next prime (21028673).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21028661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 33663 + ... + 34281.

It is an arithmetic number, because the mean of its divisors is an integer number (1085000).

Almost surely, 2^21028668 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 21028668, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26040000).

21028668 is an abundant number, since it is smaller than the sum of its proper divisors (31051332).

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

21028668 is a wasteful number, since it uses less digits than its factorization.

21028668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 794 (or 792 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 33.

The square root of 21028668 is about 4585.7025634029. The cubic root of 21028668 is about 276.0179047406.

The spelling of 21028668 in words is "twenty-one million, twenty-eight thousand, six hundred sixty-eight".