28021500 has 144 divisors (see below), whose sum is σ = 95397120. Its totient is φ = 6883200.

The previous prime is 28021421. The next prime is 28021501. The reversal of 28021500 is 512082.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28021501) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 58261 + ... + 58739.

It is an arithmetic number, because the mean of its divisors is an integer number (662480).

Almost surely, 2^28021500 is an apocalyptic number.

28021500 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 28021500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (47698560).

28021500 is an abundant number, since it is smaller than the sum of its proper divisors (67375620).

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

28021500 is a wasteful number, since it uses less digits than its factorization.

28021500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 517 (or 502 counting only the distinct ones).

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

The square root of 28021500 is about 5293.5337913345. The cubic root of 28021500 is about 303.7365995206.

Adding to 28021500 its reverse (512082), we get a palindrome (28533582).

The spelling of 28021500 in words is "twenty-eight million, twenty-one thousand, five hundred".