21028500 has 72 divisors (see below), whose sum is σ = 66352104. Its totient is φ = 5606400.

The previous prime is 21028493. The next prime is 21028517. The reversal of 21028500 is 582012.

It can be written as a sum of positive squares in 4 ways, for example, as 125316 + 20903184 = 354^2 + 4572^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

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, 2164 + ... + 6836.

It is an arithmetic number, because the mean of its divisors is an integer number (921557).

Almost surely, 2^21028500 is an apocalyptic number.

21028500 is a gapful number since it is divisible by the number (20) 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 21028500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33176052).

21028500 is an abundant number, since it is smaller than the sum of its proper divisors (45323604).

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

21028500 is a wasteful number, since it uses less digits than its factorization.

21028500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4698 (or 4683 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 18.

The square root of 21028500 is about 4585.6842455625. The cubic root of 21028500 is about 276.0171696943.

It can be divided in two parts, 21028 and 500, that added together give a triangular number (21528 = T₂₀₇).

The spelling of 21028500 in words is "twenty-one million, twenty-eight thousand, five hundred".