21728700 has 108 divisors (see below), whose sum is σ = 77859600. Its totient is φ = 4965120.

The previous prime is 21728699. The next prime is 21728719. The reversal of 21728700 is 782712.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 4576 + ... + 8024.

Almost surely, 2^21728700 is an apocalyptic number.

21728700 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 21728700, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38929800).

21728700 is an abundant number, since it is smaller than the sum of its proper divisors (56130900).

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

21728700 is a wasteful number, since it uses less digits than its factorization.

21728700 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3476 (or 3466 counting only the distinct ones).

The product of its (nonzero) digits is 1568, while the sum is 27.

The square root of 21728700 is about 4661.4053674831. The cubic root of 21728700 is about 279.0473577451.

The spelling of 21728700 in words is "twenty-one million, seven hundred twenty-eight thousand, seven hundred".