21728880 has 120 divisors (see below), whose sum is σ = 73932768. Its totient is φ = 5718528.

The previous prime is 21728867. The next prime is 21728891. The reversal of 21728880 is 8882712.

It is a tau number, because it is divible by the number of its divisors (120).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 74014 + ... + 74306.

Almost surely, 2^21728880 is an apocalyptic number.

21728880 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 21728880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36966384).

21728880 is an abundant number, since it is smaller than the sum of its proper divisors (52203888).

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

21728880 is a wasteful number, since it uses less digits than its factorization.

21728880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 415 (or 406 counting only the distinct ones).

The product of its (nonzero) digits is 14336, while the sum is 36.

The square root of 21728880 is about 4661.4246749250. The cubic root of 21728880 is about 279.0481282834.

The spelling of 21728880 in words is "twenty-one million, seven hundred twenty-eight thousand, eight hundred eighty".