21728799 has 24 divisors (see below), whose sum is σ = 34112000. Its totient is φ = 13277520.

The previous prime is 21728789. The next prime is 21728807. The reversal of 21728799 is 99782712.

It is not a de Polignac number, because 21728799 - 2⁷ = 21728671 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21728719) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3252 + ... + 7350.

Almost surely, 2^21728799 is an apocalyptic number.

21728799 is a deficient number, since it is larger than the sum of its proper divisors (12383201).

21728799 is a wasteful number, since it uses less digits than its factorization.

21728799 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4155 (or 4152 counting only the distinct ones).

The product of its digits is 127008, while the sum is 45.

The square root of 21728799 is about 4661.4159865861. The cubic root of 21728799 is about 279.0477815417.

The spelling of 21728799 in words is "twenty-one million, seven hundred twenty-eight thousand, seven hundred ninety-nine".