21728844 has 24 divisors (see below), whose sum is σ = 56334320. Its totient is φ = 7242912.

The previous prime is 21728843. The next prime is 21728849. The reversal of 21728844 is 44882712.

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

It is a junction number, because it is equal to n+sod(n) for n = 21728799 and 21728808.

It is not an unprimeable number, because it can be changed into a prime (21728843) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 100489 + ... + 100704.

Almost surely, 2^21728844 is an apocalyptic number.

It is an amenable number.

21728844 is an abundant number, since it is smaller than the sum of its proper divisors (34605476).

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

21728844 is a wasteful number, since it uses less digits than its factorization.

21728844 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 201206 (or 201198 counting only the distinct ones).

The product of its digits is 28672, while the sum is 36.

The square root of 21728844 is about 4661.4208134430. The cubic root of 21728844 is about 279.0479741761.

The spelling of 21728844 in words is "twenty-one million, seven hundred twenty-eight thousand, eight hundred forty-four".