21729760 has 96 divisors (see below), whose sum is σ = 57238272. Its totient is φ = 7741440.

The previous prime is 21729751. The next prime is 21729781. The reversal of 21729760 is 6792712.

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 15 ways as a sum of consecutive naturals, for example, 64312 + ... + 64648.

It is an arithmetic number, because the mean of its divisors is an integer number (596232).

Almost surely, 2^21729760 is an apocalyptic number.

21729760 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 21729760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28619136).

21729760 is an abundant number, since it is smaller than the sum of its proper divisors (35508512).

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

21729760 is a wasteful number, since it uses less digits than its factorization.

21729760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 396 (or 388 counting only the distinct ones).

The product of its (nonzero) digits is 10584, while the sum is 34.

The square root of 21729760 is about 4661.5190657124. The cubic root of 21729760 is about 279.0518952982.

The spelling of 21729760 in words is "twenty-one million, seven hundred twenty-nine thousand, seven hundred sixty".