21728130 has 48 divisors (see below), whose sum is σ = 53410752. Its totient is φ = 5656000.

The previous prime is 21728129. The next prime is 21728143. The reversal of 21728130 is 3182712.

It is a super-2 number, since 2×21728130² = 944223266593800, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21728130.

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, 215080 + ... + 215180.

It is an arithmetic number, because the mean of its divisors is an integer number (1112724).

Almost surely, 2^21728130 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21728130, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26705376).

21728130 is an abundant number, since it is smaller than the sum of its proper divisors (31682622).

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

21728130 is a wasteful number, since it uses less digits than its factorization.

21728130 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 283 (or 182 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 21728130 is about 4661.3442267226. The cubic root of 21728130 is about 279.0449176791.

The spelling of 21728130 in words is "twenty-one million, seven hundred twenty-eight thousand, one hundred thirty".