21903728 has 80 divisors (see below), whose sum is σ = 55282176. Its totient is φ = 8152320.

The previous prime is 21903719. The next prime is 21903733. The reversal of 21903728 is 82730912.

It is a junction number, because it is equal to n+sod(n) for n = 21903694 and 21903703.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 27950 + ... + 28722.

Almost surely, 2^21903728 is an apocalyptic number.

21903728 is a gapful number since it is divisible by the number (28) 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 21903728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27641088).

21903728 is an abundant number, since it is smaller than the sum of its proper divisors (33378448).

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

21903728 is a wasteful number, since it uses less digits than its factorization.

21903728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 822 (or 816 counting only the distinct ones).

The product of its (nonzero) digits is 6048, while the sum is 32.

The square root of 21903728 is about 4680.1418781913. The cubic root of 21903728 is about 279.7946112826.

The spelling of 21903728 in words is "twenty-one million, nine hundred three thousand, seven hundred twenty-eight".