21728250 has 160 divisors (see below), whose sum is σ = 64555920. Its totient is φ = 5443200.

The previous prime is 21728249. The next prime is 21728269. The reversal of 21728250 is 5282712.

It can be written as a sum of positive squares in 8 ways, for example, as 3606201 + 18122049 = 1899^2 + 4257^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 587232 + ... + 587268.

Almost surely, 2^21728250 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21728250, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32277960).

21728250 is an abundant number, since it is smaller than the sum of its proper divisors (42827670).

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

21728250 is a wasteful number, since it uses less digits than its factorization.

21728250 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 95 (or 76 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21728250 is about 4661.3570985283. The cubic root of 21728250 is about 279.0454313808.

The spelling of 21728250 in words is "twenty-one million, seven hundred twenty-eight thousand, two hundred fifty".