21729224 has 16 divisors (see below), whose sum is σ = 44446320. Its totient is φ = 9876880.

The previous prime is 21729199. The next prime is 21729229. The reversal of 21729224 is 42292712.

It is not an unprimeable number, because it can be changed into a prime (21729229) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 123374 + ... + 123549.

It is an arithmetic number, because the mean of its divisors is an integer number (2777895).

Almost surely, 2^21729224 is an apocalyptic number.

It is an amenable number.

21729224 is an abundant number, since it is smaller than the sum of its proper divisors (22717096).

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

21729224 is a wasteful number, since it uses less digits than its factorization.

21729224 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 246940 (or 246936 counting only the distinct ones).

The product of its digits is 4032, while the sum is 29.

The square root of 21729224 is about 4661.4615733695. The cubic root of 21729224 is about 279.0496008558.

The spelling of 21729224 in words is "twenty-one million, seven hundred twenty-nine thousand, two hundred twenty-four".